Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

3 files changed, 1418 insertions, 0 deletions

diff --git a/testing/web-platform/tests/png/apng/resources/README.md b/testing/web-platform/tests/png/apng/resources/README.md
new file mode 100644
index 0000000000..ecd61795b1
--- /dev/null
+++ b/testing/web-platform/tests/png/apng/resources/README.md
@@ -0,0 +1,14 @@
+# Regenerating APNG Test Images
+
+## Test images
+
+Most of the APNG tests are a port to WPT of an [earlier testsuite by Philip Taylor](https://philip.html5.org/tests/apng/tests.html). The test images were autogenerated, and this directory contains what is needed to regenerate them:
+
+- ['source.html'](./source.html) which contains a human-readable description of each test file
+- ['generate.pl'](./generate.pl) which uses [Cairo](https://www.cairographics.org/) to create the test images
+
+If this script is used to create additional images, not part of the original test suite, be aware that the generated files are automatically named as sequentially-numbered `nnn.png` so add any new ones _at the end_ to avoid changing the name of existing files.
+
+## Reference images
+
+The reference images were created by decompiling the APNG with [apngasm](https://github.com/apngasm/apngasm) into a series of static PNG representing the displayed state of each frame. The last one therefore represents the end state of the animation. Again this tool produces numbered files like `nn.png` so these were renamed in a more meaningful way (such as `darkblue.png`) to create the reference images.
diff --git a/testing/web-platform/tests/png/apng/resources/generate.pl b/testing/web-platform/tests/png/apng/resources/generate.pl
new file mode 100644
index 0000000000..631356fb7e
--- /dev/null
+++ b/testing/web-platform/tests/png/apng/resources/generate.pl
@@ -0,0 +1,390 @@
+=pod
+Copyright (c) 2007 Philip Taylor
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+=cut
+
+use strict;
+use warnings;
+
+use Compress::Zlib();
+use Cairo;
+use PDL qw(float byte);
+
+sub chunk {
+    my ($name, $data) = @_;
+    (pack 'N', length $data) . $name . $data . (pack 'N', Compress::Zlib::crc32($name . $data));
+}
+
+sub IHDR {
+    my ($img) = @_;
+    return chunk 'IHDR', pack 'NNCCCCC',
+        $img->{width}, $img->{height},
+        $img->{bit_depth}, $img->{color_type},
+        $img->{compression_method}, $img->{filter_method}, $img->{interlace_method};
+}
+
+sub gAMA {
+    my ($img) = @_;
+    return chunk 'gAMA', pack 'N', $img->{gamma};
+}
+
+sub sRGB {
+    my ($img) = @_;
+    return chunk 'sRGB', pack 'C', $img->{rendering_intent};
+}
+
+sub PLTE {
+    my ($img) = @_;
+    return chunk 'PLTE', pack 'C*', @{$img->{colours}};
+}
+
+sub tRNS {
+    my ($img) = @_;
+    return chunk 'tRNS', pack 'C*', @{$img->{values}};
+}
+
+sub IDAT {
+    my ($img) = @_;
+    return chunk 'IDAT', xdat_data($img);
+}
+
+sub IDAT_split {
+    my ($img, $blocksize) = @_;
+    my $c = xdat_data($img);
+    my @out;
+    while (length $c) {
+        push @out, chunk 'IDAT', substr $c, 0, $blocksize, '';
+    }
+    return @out;
+}
+
+sub IEND {
+    my ($img) = @_;
+    return chunk 'IEND', '';
+}
+
+sub acTL {
+    my ($img) = @_;
+    return chunk 'acTL', pack 'NN', $img->{num_frames}, $img->{num_plays};
+}
+
+sub fcTL {
+    my ($img) = @_;
+    return chunk 'fcTL', pack 'NNNNNnnCC',
+        $img->{sequence_number},
+        $img->{width}, $img->{height},
+        $img->{x_offset}, $img->{y_offset},
+        $img->{delay_num}, $img->{delay_den},
+        $img->{dispose_op}, $img->{blend_op};
+}
+
+sub fdAT {
+    my ($img) = @_;
+    return chunk 'fdAT', (pack 'N', $img->{sequence_number}) . xdat_data($img);
+}
+
+sub xdat_data {
+    my ($img) = @_;
+    return compress(filter($img->{image_data}, $img->{width}, $img->{height}, $img->{depth}));
+}
+
+use constant DISPOSE_NONE => 0;
+use constant DISPOSE_BACKGROUND => 1;
+use constant DISPOSE_PREVIOUS => 2;
+use constant BLEND_SOURCE => 0;
+use constant BLEND_OVER => 1;
+
+sub filter {
+    my ($imagedata, $width, $height, $depth) = @_;
+    my $out = '';
+    for my $scanline (0..$height-1) {
+        $out .= pack 'C', 0;
+        $out .= substr($imagedata, $scanline*$width*$depth/8, $width*$depth/8);
+    }
+    return $out;
+}
+
+sub compress {
+    my ($filtered) = @_;
+    return Compress::Zlib::compress($filtered);
+}
+
+
+sub fix_bitmap {
+    my ($d) = @_;
+    # Flip BGRA->RGBA, and undo premultiplication
+
+    my $pdl = float unpack 'C*', $d;
+    my $pdl2 = byte $pdl;
+    my $a = 255 / $pdl->mslice([3, -1, 4]);
+    $pdl2->mslice([0, -1, 4]) .= $pdl->mslice([2, -1, 4])*$a;
+    $pdl2->mslice([1, -1, 4]) .= $pdl->mslice([1, -1, 4])*$a;
+    $pdl2->mslice([2, -1, 4]) .= $pdl->mslice([0, -1, 4])*$a;
+    return ${(byte $pdl2)->get_dataref};
+=pod
+    my @d = unpack 'C*', $d;
+    my $a;
+    for (map $_*4, 0..$#d/4) {
+        if ($a = $d[$_+3]) {
+            $a = 255 / $a;
+            @d[$_, $_+1, $_+2] = ($d[$_+2]*$a, $d[$_+1]*$a, $d[$_]*$a);
+        } # else alpha=0 hence r=g=b=0, so nothing to do
+    }
+    return pack 'C*', @d;
+=cut
+}
+
+sub create_surface {
+    my ($w, $h, $type, @data) = @_;
+    my $surface = Cairo::ImageSurface->create('argb32', $w, $h);
+    my $cr = Cairo::Context->create($surface);
+
+    if ($type eq 'red') {
+        ($type, @data) = ('solid', 1, 0, 0, 1);
+    } elsif ($type eq 'green') {
+        ($type, @data) = ('solid', 0, 1, 0, 1);
+    } elsif ($type eq 'blue') {
+        ($type, @data) = ('solid', 0, 0, 1, 1);
+    } elsif ($type eq 'cyan') {
+        ($type, @data) = ('solid', 0, 1, 1, 1);
+    } elsif ($type eq 'magenta') {
+        ($type, @data) = ('solid', 1, 0, 1, 1);
+    } elsif ($type eq 'yellow') {
+        ($type, @data) = ('solid', 1, 1, 0, 1);
+    } elsif ($type eq 'transparent') {
+        ($type, @data) = ('solid', 0, 0, 0, 0);
+    }
+
+    if ($type eq 'solid') {
+        $cr->rectangle(0, 0, $w, $h);
+        $cr->set_source_rgba(@data);
+        $cr->fill;
+    } elsif ($type eq 'doublerect') {
+        $cr->rectangle(0, 0, $w, $h);
+        $cr->set_source_rgba(@data[0..3]);
+        $cr->fill;
+        $cr->rectangle(int($w/4), int($h/4), int($w/2), int($h/2));
+        $cr->set_source_rgba(@data[4..7]);
+        $cr->fill;
+    } else {
+        die "Invalid create_surface type '$type'";
+    }
+    return { width => $w, height => $h, depth => 32, data => fix_bitmap($surface->get_data) };
+}
+
+sub create_raw_surface {
+    my ($w, $h, $d, $data) = @_;
+    return { width => $w, height => $h, depth => $d, data => $data };
+}
+
+sub find_errors {
+    my (@img) = @_;
+    my @chunks;
+    {
+        my @img2 = @img;
+        push @chunks, [ splice @img2, 0, 2 ] while @img2;
+    }
+
+    my $chunknames = join '', map "<$_->[0]>", @chunks;
+
+    my @errors;
+
+    my $has_actl = ($chunknames =~ /<acTL>/);
+
+    if ($has_actl) {
+        # acTL must be before IDAT
+        if ($chunknames =~ /<IDAT>.*<acTL>/) {
+            push @errors, "acTL after IDAT";
+        }
+
+        # Must have only one acTL (TODO: in spec?)
+        if ($chunknames =~ /<acTL>.*<acTL>/) {
+            push @errors, "More than one acTL";
+        }
+
+        my $num_frames = {@img}->{acTL}[0];
+
+        # num_frames > 0
+        if ($num_frames <= 0) {
+            push @errors, "num_frames <= 0";
+        }
+
+        # num_frames = count(fcTL)
+        my $num_fctls = grep $_->[0] eq 'fcTL', @chunks;
+        if ($num_frames != $num_fctls) {
+            push @errors, "num_frames ($num_frames) != number of fcTLs ($num_fctls)";
+        }
+    }
+
+    # Check sequence numbers (start from 0, no duplicates or gaps)
+    my @seqnos;
+    for (grep { $_->[0] =~ /^(fcTL|fdAT|fdAT_split)$/ } @chunks) {
+        push @seqnos, $_->[1][0];
+    }
+    if (@seqnos and (join ',', @seqnos) ne (join ',', 0..$#seqnos)) {
+        push @errors, "Incorrect sequence numbers";
+    }
+
+    return @errors;
+}
+
+sub create_image {
+    my ($filename, @img) = @_;
+    my @chunks;
+    while (@img) {
+        my ($chunk, $data) = splice @img, 0, 2;
+        if ($chunk eq 'IHDR') {
+            push @chunks, IHDR {
+                width => $data->[0],
+                height => $data->[1],
+                bit_depth => defined $data->[2] ? $data->[2] : 8,
+                color_type => defined $data->[3] ? $data->[3] : 6,
+                compression_method => 0,
+                filter_method => 0,
+                interlace_method => 0,
+            };
+        } elsif ($chunk eq 'IEND') {
+            push @chunks, IEND { }
+        } elsif ($chunk eq 'gAMA') {
+            push @chunks, gAMA {
+                gamma => int(100_000*$data->[0]),
+            };
+        } elsif ($chunk eq 'sRGB') {
+            push @chunks, sRGB {
+                rendering_intent => $data->[0],
+            };
+        } elsif ($chunk eq 'PLTE') {
+            push @chunks, PLTE {
+                colours => $data,
+            };
+        } elsif ($chunk eq 'tRNS') {
+            push @chunks, tRNS {
+                values => $data,
+            };
+        } elsif ($chunk eq 'acTL') {
+            push @chunks, acTL {
+                num_frames => $data->[0],
+                num_plays => $data->[1],
+            };
+        } elsif ($chunk eq 'fcTL') {
+            push @chunks, fcTL {
+                sequence_number => $data->[0],
+                width => $data->[1],
+                height => $data->[2],
+                x_offset => $data->[3],
+                y_offset => $data->[4],
+                delay_num => $data->[5],
+                delay_den => $data->[6],
+                dispose_op => $data->[7],
+                blend_op => $data->[8],
+            };
+        } elsif ($chunk eq 'IDAT') {
+            push @chunks, IDAT {
+                depth => $data->[0]{depth},
+                width => $data->[0]{width},
+                height => $data->[0]{height},
+                image_data => $data->[0]{data},
+            }
+        } elsif ($chunk eq 'IDAT_split') {
+            my $c = xdat_data {
+                depth => $data->[2]{depth},
+                width => $data->[2]{width},
+                height => $data->[2]{height},
+                image_data => $data->[2]{data},
+            };
+            if ($data->[1] == -1) {
+                $c = substr $c, $data->[0];
+            } else {
+                $c = substr $c, $data->[0], $data->[1] - $data->[0];
+            }
+            push @chunks, chunk 'IDAT', $c;
+        } elsif ($chunk eq 'fdAT') {
+            push @chunks, fdAT {
+                sequence_number => $data->[0],
+                depth => $data->[1]{depth},
+                width => $data->[1]{width},
+                height => $data->[1]{height},
+                image_data => $data->[1]{data},
+            }
+        } elsif ($chunk eq 'fdAT_split') {
+            my $c = xdat_data {
+                depth => $data->[3]{depth},
+                width => $data->[3]{width},
+                height => $data->[3]{height},
+                image_data => $data->[3]{data},
+            };
+            if ($data->[2] == -1) {
+                $c = substr $c, $data->[1];
+            } else {
+                $c = substr $c, $data->[1], $data->[2] - $data->[1];
+            }
+            push @chunks, chunk 'fdAT', (pack 'N', $data->[0]) . $c;
+        } else {
+            die "Invalid create_image chunk '$chunk'";
+        }
+    }
+    open my $fh, '>', "images/$filename.png" or die $!;
+    binmode $fh;
+    print $fh "\211PNG\r\n\032\n", @chunks;
+}
+
+use constant W => 128;
+use constant H => 64;
+
+sub escape_html {
+    my ($t) = @_;
+    $t =~ s/&/&amp;/g;
+    $t =~ s/</&lt;/g;
+    return $t;
+}
+
+my $img_id = '000';
+sub handle_html_png {
+    my ($code) = @_;
+    my $name = $img_id++;
+    my @img = eval '(' . $code . ')';
+    die $@ if $@;
+    create_image($name, @img);
+    my $data = $code;
+    $data =~ s/^\s*(.*?)\s*$/$1/sg;
+    $data =~ s/([^a-zA-Z0-9])/sprintf('%%%02X', ord $1)/eg;
+    my $errors = (join '; ', map escape_html($_), find_errors(@img)) || 'None';
+    return qq{<p>}
+        #. qq{<object data="$name.png" class="testimage"><strong>Did not load image.</strong></object>} # IE doesn't like this
+        . qq{<img src="$name.png" alt="Did not load image" class="testimage">\n}
+        . qq{<p><a href="data:text/plain,$data">(source)</a>\n}
+        #. qq{<p>Expected errors: $errors\n}
+        ;
+}
+# TODO: regexping HTML is nasty - should use a better input data format instead
+sub handle_html_case {
+    my ($title) = @_;
+    my $id = lc $title;
+    $id =~ s/[^a-z0-9]+/-/g;
+    $id =~ s/^-*(.*?)-*$/$1/g;
+    return qq{<div class="case" id="$id">\n<p><a href="#$id">#</a> $title\n};
+}
+
+open my $in, 'source.html' or die $!;
+my $html = do { local $/; <$in> };
+$html =~ s/<png>(.*?)<\/png>/handle_html_png($1)/seg;
+$html =~ s/<div class="case">\n<p>(.*?)\n/handle_html_case($1)/eg;
+open my $out, '>', 'images/tests.html' or die $!;
+print $out $html;
\ No newline at end of file
diff --git a/testing/web-platform/tests/png/apng/resources/source.html b/testing/web-platform/tests/png/apng/resources/source.html
new file mode 100644
index 0000000000..cca7063cff
--- /dev/null
+++ b/testing/web-platform/tests/png/apng/resources/source.html
@@ -0,0 +1,1014 @@
+<!DOCTYPE HTML>
+<title>APNG tests</title>
+<style>
+html {
+    background-color: white;
+    color: black;
+}
+body {
+    font-family: sans-serif;
+}
+.testimage {
+    border: 1px black solid;
+    background: #ffa;
+}
+blockquote {
+    font-style: italic;
+}
+blockquote[cite]:after {
+    font-style: normal;
+    font-size: x-small;
+    padding-left: 2em;
+    content: "(" attr(cite) ")";
+}
+blockquote[cite="#apng"]:after {
+    content: "(APNG Specification)";
+}
+blockquote[cite="#png"]:after {
+    content: "(PNG Specification)";
+}
+blockquote p {
+    margin: 0;
+}
+div.case {
+    border: 1px #888 solid;
+    padding: 0.3em;
+    margin: 0.3em;
+}
+div.case:target {
+    border: 2px #000 solid;
+}
+div.case > p {
+    margin: 0;
+}
+</style>
+
+<p><em>This page is somewhat incomplete and quite possibly incorrect &ndash; use with caution. <img src="underconstruction.png" style="vertical-align: middle" alt=""></em>
+
+<h1>APNG tests</h1>
+
+<p>For all these tests, wait at least a second after all the images have downloaded, before checking that the rendered output is correct.
+
+<p>Test output conventions:
+A solid green 128&times;64 rectangle means success.
+Any red means failure.
+Anything else means you need to read the instructions.
+"Transparent" is indicated by a <span style="background: #ffa">light yellow background</span>.
+
+<p>Sections of the relevant specifications are sometimes quoted when they clarify the expected behaviour.
+
+<p>Please don't link directly to the images in this page, since they may get renamed and will break any such links.
+
+<p>You can download <a href="generate.pl">the script</a> and <a href="source.html">the source data</a> for this page.
+
+
+<h2>Valid images</h2>
+
+
+<h3>Basic cases</h3>
+
+<div class="case">
+<p>Trivial static image.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+IDAT => [create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Trivial animated image - one frame; using default image.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Trivial animated image - one frame; ignoring default image.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>IDAT, fdAT splitting</h3>
+<blockquote cite="#png"><p>There may be multiple IDAT chunks; if so, they shall appear consecutively with no other intervening chunks. The compressed datastream is then the concatenation of the contents of the data fields of all the IDAT chunks.</blockquote>
+<blockquote cite="#apng"><p>The compressed datastream is then the concatenation of the contents of the data fields of all the `fdAT` chunks within a frame.</blockquote>
+
+<div class="case">
+<p>Basic split IDAT.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+IDAT_split => [0,32, create_surface(W, H, 'green')],
+IDAT_split => [32,-1, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Split IDAT with zero-length chunk.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+IDAT_split => [0,32, create_surface(W, H, 'green')],
+IDAT_split => [32,32, create_surface(W, H, 'green')],
+IDAT_split => [32,-1, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Basic split fdAT.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT_split => [1, 0,32, create_surface(W, H, 'green')],
+fdAT_split => [2, 32,-1, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Split fdAT with zero-length chunk.
+<p>This should be solid green.
+<!-- Opera bug 286566 -->
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT_split => [1, 0,32, create_surface(W, H, 'green')],
+fdAT_split => [2, 32,32, create_surface(W, H, 'green')],
+fdAT_split => [3, 32,-1, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>Dispose ops</h3>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_NONE - basic.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [3, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [1, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'green')],
+fcTL => [3, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [4, create_surface(W, H, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_BACKGROUND - basic.
+<p>This should be transparent.
+<png>
+IHDR => [W, H],
+acTL => [3, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [1, W, H, 0, 0, 10, 100, DISPOSE_BACKGROUND, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'red')],
+fcTL => [3, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [4, create_surface(W, H, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_BACKGROUND - final frame.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [1, W, H, 0, 0, 10, 100, DISPOSE_BACKGROUND, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_PREVIOUS - basic.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [3, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'green')],
+fcTL => [2, W, H, 0, 0, 10, 100, DISPOSE_PREVIOUS, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'red')],
+fcTL => [4, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [5, create_surface(W, H, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_PREVIOUS - final frame.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [1, W, H, 0, 0, 10, 100, DISPOSE_PREVIOUS, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_PREVIOUS - first frame.
+<p>This should be transparent.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_PREVIOUS, BLEND_OVER],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [1, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>Dispose ops and regions</h3>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_NONE in region.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [3, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H, 'doublerect', 0,1,0,1, 1,0,0,1)],
+fcTL => [1, W/2, H/2, W/4, H/4, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W/2, H/2, 'green')],
+fcTL => [3, 1, 1, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [4, create_surface(1, 1, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_BACKGROUND before region.
+<p>This should be transparent.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_BACKGROUND, BLEND_OVER],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [1, 1, 1, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(1, 1, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_BACKGROUND in region.
+<p>This should be a solid blue rectangle containing a smaller transparent rectangle.
+<!-- Opera bug 286565 -->
+<png>
+IHDR => [W, H],
+acTL => [3, 1],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H, 'doublerect', 0,0,1,1, 1,0,0,1)],
+fcTL => [1, W/2, H/2, W/4, H/4, 10, 100, DISPOSE_BACKGROUND, BLEND_OVER],
+fdAT => [2, create_surface(W/2, H/2, 'red')],
+fcTL => [3, 1, 1, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [4, create_surface(1, 1, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_DISPOSE_OP_PREVIOUS in region.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [3, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'green')],
+fcTL => [2, W/2, H/2, W/4, H/4, 10, 100, DISPOSE_PREVIOUS, BLEND_OVER],
+fdAT => [3, create_surface(W/2, H/2, 'red')],
+fcTL => [4, 1, 1, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [5, create_surface(1, 1, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>Blend ops</h3>
+
+<div class="case">
+<p>APNG_BLEND_OP_SOURCE on solid colour.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_SOURCE],
+fdAT => [3, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_BLEND_OP_SOURCE on transparent colour.
+<p>This should be transparent.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_SOURCE],
+fdAT => [3, create_surface(W, H, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_BLEND_OP_SOURCE on nearly-transparent colour.
+<p>This should be very nearly transparent.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_SOURCE],
+fdAT => [3, create_surface(W, H, 'solid', 0, 1, 0, 0.01)],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_BLEND_OP_OVER on solid and transparent colours.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'green')],
+fcTL => [2, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'transparent')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_BLEND_OP_OVER repeatedly with nearly-transparent colours.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+acTL => [128, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'solid', 0, 1, 0, 1)],
+(map {
+    (fcTL => [2+$_*2, W/2, H, 0, 0, 1, 100, DISPOSE_NONE, BLEND_OVER],
+    fdAT => [3+$_*2, create_surface(W/2, H, 'solid', 0, 1, 0, 0.01)])
+} 0..126),
+IEND => [],
+</png>
+</div>
+
+
+<h3>Blending and gamma</h3>
+
+<div class="case">
+<p>APNG_BLEND_OP_OVER
+<p>This should be solid slightly-dark green.
+<png>
+IHDR => [W, H],
+gAMA => [1],
+acTL => [16, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'solid', 0, 1, 0, 1)],
+(map {
+    (fcTL => [2+$_*2, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+    fdAT => [3+$_*2, create_surface(W, H, 'solid', 0, 0.9, 0, 0.5)])
+} 0..14),
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>APNG_BLEND_OP_OVER
+<p>This should be solid nearly-black.
+<png>
+IHDR => [W, H],
+gAMA => [1/2200],
+acTL => [16, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+(map {
+    (fcTL => [2+$_*2, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+    fdAT => [3+$_*2, create_surface(W, H, 'solid', 0.9, 0, 0, 0.5)])
+} 0..14),
+IEND => [],
+</png>
+</div>
+
+
+<h3>Chunk ordering</h3>
+
+<div class="case">
+<p>fcTL before acTL.
+<p>This should be solid green.
+<png>
+IHDR => [W, H],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+acTL => [2, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [1, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>Delays</h3>
+
+<div class="case">
+<p>Basic delays.
+<p>This should flash blue for half a second, then yellow for one second, then repeat.
+<png>
+IHDR => [W, H],
+acTL => [4, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 50, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'blue')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'yellow')],
+fcTL => [4, W, H, 0, 0, 10000, 20000, DISPOSE_NONE, BLEND_OVER],
+fdAT => [5, create_surface(W, H, 'blue')],
+fcTL => [6, W, H, 0, 0, 1, 1, DISPOSE_NONE, BLEND_OVER],
+fdAT => [7, create_surface(W, H, 'yellow')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Rounding of division.
+<p>This should flash blue for half a second, then yellow for one second, then repeat.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 1, 2, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'blue')],
+fcTL => [2, W, H, 0, 0, 1, 1, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'yellow')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>16-bit numerator/denominator.
+<p>This should flash blue for half a second, then yellow for one second, then repeat.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 32767, 65534, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'blue')],
+fcTL => [2, W, H, 0, 0, 65535, 65535, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'yellow')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Zero denominator.
+<blockquote cite="#apng"><p>If the denominator is 0, it is to be treated as if it were 100</blockquote>
+<p>This should flash blue for half a second, then yellow for one second, then repeat.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 50, 0, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'blue')],
+fcTL => [2, W, H, 0, 0, 1000, 1000, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'yellow')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Zero numerator.
+<blockquote cite="#apng"><p>If the the value of the numerator is 0 the decoder should render the next frame as quickly as possible, though viewers may impose a reasonable lower bound.</blockquote>
+<p>This should flash cyan for a short period of time (perhaps zero), then magenta for the same short period of time, then blue for half a second, then yellow for one second, then repeat.
+<png>
+IHDR => [W, H],
+acTL => [4, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 0, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'cyan')],
+fcTL => [2, W, H, 0, 0, 0, 0, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'magenta')],
+fcTL => [4, W, H, 0, 0, 500, 1000, DISPOSE_NONE, BLEND_OVER],
+fdAT => [5, create_surface(W, H, 'blue')],
+fcTL => [6, W, H, 0, 0, 1000, 1000, DISPOSE_NONE, BLEND_OVER],
+fdAT => [7, create_surface(W, H, 'yellow')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>num_plays</h3>
+
+<div class="case">
+<p>num_plays = 0
+<p>This should flash yellow for one second, then blue for one second, then repeat forever.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'yellow')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'blue')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>num_plays = 1
+<p>When first loaded, this should flash yellow for one second, then stay blue forever.
+<png>
+IHDR => [W, H],
+acTL => [2, 1],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'yellow')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'blue')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>num_plays = 2
+<p>When first loaded, this should flash yellow for one second, then blue for one second, then yellow for one second, then blue forever.
+<png>
+IHDR => [W, H],
+acTL => [2, 2],
+IDAT => [create_surface(W, H, 'red')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'yellow')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'blue')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>Other depths and colour types</h3>
+
+<div class="case">
+<p>16-bit colour.
+<p>This should be dark blue.
+<png>
+IHDR => [W, H, 16, 6],
+acTL => [2, 1],
+IDAT => [create_raw_surface(W, H, 64, "\xFF\x00\x00\x00\x00\x00\xFF\xFF" x (W*H))],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_raw_surface(W, H, 64, "\x00\x00\x00\x00\x00\x00\xFF\xFF" x (W*H))],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_raw_surface(W, H, 64, "\x00\x00\x00\x00\xFF\xFF\x80\x00" x (W*H))],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>8-bit greyscale.
+<p>This should be a solid grey rectangle containing a solid white rectangle.
+<png>
+IHDR => [W, H, 8, 0],
+acTL => [2, 1],
+IDAT => [create_raw_surface(W, H, 8, "\x00\xFF" x (W*H/2))],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_raw_surface(W, H, 8, "\x80" x (W*H))],
+fcTL => [2, W/2, H/2, W/4, H/4, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_raw_surface(W/2, H/2, 8, "\xFF" x (W*H/4))],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>8-bit greyscale and alpha, with blending.
+<p>This should be solid grey.
+<png>
+IHDR => [W, H, 8, 4],
+acTL => [2, 1],
+IDAT => [create_raw_surface(W, H, 16, "\x00\xFF\xFF\xFF" x (W*H/2))],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_raw_surface(W, H, 16, "\x00\xFF" x (W*H))],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_raw_surface(W, H, 16, "\xFF\x80" x (W*H))],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>2-color palette.
+<p>This should be solid green.
+<png>
+IHDR => [W, H, 1, 3],
+PLTE => [255,0,0, 0,255,0],
+acTL => [2, 1],
+IDAT => [create_raw_surface(W, H, 1, "\x00" x (W*H/8))],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_raw_surface(W, H, 1, "\x00" x (W*H/8))],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_raw_surface(W, H, 1, "\xFF" x (W*H/8))],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>2-bit palette and alpha.
+<p>This should be solid green.
+<png>
+IHDR => [W, H, 2, 3],
+PLTE => [255,0,0, 255,0,0, 0,255,0],
+tRNS => [255, 0, 255],
+acTL => [2, 1],
+IDAT => [create_raw_surface(W, H, 2, "\x00" x (W*H/4))],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_raw_surface(W, H, 2, "\xAA" x (W*H/4))],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_raw_surface(W, H, 2, "\x55" x (W*H/4))],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>1-bit palette and alpha, with blending.
+<p>This should be solid dark blue.
+<png>
+IHDR => [W, H, 1, 3],
+PLTE => [0,0,0, 0,0,255],
+tRNS => [255, 128],
+acTL => [2, 1],
+IDAT => [create_raw_surface(W, H, 1, "\x00" x (W*H/8))],
+fcTL => [0, W, H, 0, 0, 10, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_raw_surface(W, H, 1, "\x00" x (W*H/8))],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_raw_surface(W, H, 1, "\xFF" x (W*H/8))],
+IEND => [],
+</png>
+</div>
+
+
+<h2>Invalid images</h2>
+
+<blockquote cite="#apng">
+<p>It is strongly recommended that when any error is encountered decoders should discard all subsequent frames, stop the animation, and revert to displaying the default image. A decoder which detects an error before the animation has started should display the default image. An error message may be displayed to the user if appropriate.
+</blockquote>
+<p>(If some decoders accept broken images, it seems quite possible that people will create and distribute broken images, and then the error-handling would have to be reverse-engineered by other implementations; hence all these tests to ensure errors get detected properly.)
+<p>For the following images, the default image (solid green) or an error should be displayed.
+
+
+<h3>Incorrect chunks</h3>
+
+<div class="case">
+<p>Missing acTL.
+<png>
+IHDR => [W, H],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Repeated acTL.
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>acTL after IDAT.
+<png>
+IHDR => [W, H],
+IDAT => [create_surface(W, H, 'green')],
+acTL => [1, 0],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Missing fcTL.
+<p><em>Disabled for now, since it crashes Opera 9.5 alpha 1589 (bug 287173).</em>
+<!--
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'green')],
+fdAT => [0, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+-->
+</div>
+
+<div class="case">
+<p>Repeated fcTL.
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Missing fdAT.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fcTL => [1, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>num_frames</h3>
+
+<div class="case">
+<p>num_frames = 0; no default image.
+<blockquote cite="#apng"><p>0 is not a valid value.</blockquote>
+<png>
+IHDR => [W, H],
+acTL => [0, 0],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>num_frames = 0; ignoring default image.
+<blockquote cite="#apng"><p>0 is not a valid value.</blockquote>
+<png>
+IHDR => [W, H],
+acTL => [0, 0],
+IDAT => [create_surface(W, H, 'green')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>num_frames too low.
+<blockquote cite="#apng"><p>This must equal the number of `fcTL` chunks. ... If this value does not equal the actual number of frames it should be treated as an error.</blockquote>
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>num_frames too high by 1.
+<blockquote cite="#apng"><p>This must equal the number of `fcTL` chunks. ... If this value does not equal the actual number of frames it should be treated as an error.</blockquote>
+<png>
+IHDR => [W, H],
+acTL => [3, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>num_frames too high by 2.
+<blockquote cite="#apng"><p>This must equal the number of `fcTL` chunks. ... If this value does not equal the actual number of frames it should be treated as an error.</blockquote>
+<png>
+IHDR => [W, H],
+acTL => [4, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>num_frames outside valid range.
+<blockquote cite="#apng"><p>an "unsigned int" shall be a 32-bit unsigned integer in network byte order limited to the range 0 to (2^31)-1</blockquote>
+<png>
+IHDR => [W, H],
+acTL => [0x80000001, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>Sequence numbers</h3>
+
+<div class="case">
+<p>Not starting from 0.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [1, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'red')],
+fcTL => [3, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [4, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Gap in sequence.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [4, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Duplicated sequence number.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Duplicated chunk.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [3, create_surface(W, H, 'red')],
+fdAT => [3, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Reordered fdAT chunks.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT_split => [4, 32,-1, create_surface(W, H, 'red')],
+fdAT_split => [3, 0,32, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Reordered sequence numbers.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+fcTL => [2, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT_split => [4, 0,32, create_surface(W, H, 'red')],
+fdAT_split => [3, 32,-1, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>Separated fdAT and fcTL sequences.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [0, create_surface(W, H, 'red')],
+fcTL => [1, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+
+<h3>Invalid image-data sizes</h3>
+
+<div class="case">
+<p>Default image's fcTL size not matching IHDR.
+<png>
+IHDR => [W, H],
+acTL => [2, 0],
+fcTL => [0, W, H/2, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+IDAT => [create_surface(W, H/2, 'red')],
+fcTL => [1, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [2, create_surface(W, H, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>fdAT too small.
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H/2, 'red')],
+IEND => [],
+</png>
+</div>
+
+<div class="case">
+<p>fdAT too large.
+<png>
+IHDR => [W, H],
+acTL => [1, 0],
+IDAT => [create_surface(W, H, 'green')],
+fcTL => [0, W, H, 0, 0, 100, 100, DISPOSE_NONE, BLEND_OVER],
+fdAT => [1, create_surface(W, H*2, 'red')],
+IEND => [],
+</png>
+</div>
+
+<!-- TODO: invalid fcTL (negative offset, etc) -->
+
+<h2>References</h2>
+<ul>
+<li id="apng"><a href="http://wiki.mozilla.org/index.php?title=APNG_Specification&amp;oldid=64503">APNG Specification 1.0</a>
+<li id="png"><a href="http://www.w3.org/TR/PNG/">PNG Specification (Second Edition)</a>
+</ul>
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