Adding upstream version 2.10.36.upstream/2.10.36

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

1 files changed, 148 insertions, 0 deletions

diff --git a/plug-ins/file-jpeg/jpeg-quality.c b/plug-ins/file-jpeg/jpeg-quality.c
new file mode 100644
index 0000000..52bd2c7
--- /dev/null
+++ b/plug-ins/file-jpeg/jpeg-quality.c
@@ -0,0 +1,148 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * jpeg-quality.c
+ * Copyright (C) 2007 Raphaël Quinet <raphael@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <glib/gstdio.h>
+
+#include <jpeglib.h>
+
+#include "jpeg-quality.h"
+
+/*
+ * Note that although 0 is a valid quality for IJG's JPEG library, the
+ * baseline quantization tables for quality 0 and 1 are identical (all
+ * divisors are set to the maximum value 255).  So 0 can be used here
+ * to flag unusual settings.
+ */
+
+/* sum of the luminance divisors for quality = 0..100 (IJG standard tables) */
+static gint std_luminance_sum[101] =
+{
+  G_MAXINT,
+  16320, 16315, 15946, 15277, 14655, 14073, 13623, 13230, 12859, 12560, 12240,
+  11861, 11456, 11081, 10714, 10360, 10027,  9679,  9368,  9056,  8680,  8331,
+   7995,  7668,  7376,  7084,  6823,  6562,  6345,  6125,  5939,  5756,  5571,
+   5421,  5240,  5086,  4976,  4829,  4719,  4616,  4463,  4393,  4280,  4166,
+   4092,  3980,  3909,  3835,  3755,  3688,  3621,  3541,  3467,  3396,  3323,
+   3247,  3170,  3096,  3021,  2952,  2874,  2804,  2727,  2657,  2583,  2509,
+   2437,  2362,  2290,  2211,  2136,  2068,  1996,  1915,  1858,  1773,  1692,
+   1620,  1552,  1477,  1398,  1326,  1251,  1179,  1109,  1031,   961,   884,
+    814,   736,   667,   592,   518,   441,   369,   292,   221,   151,    86,
+     64
+};
+
+/* sum of the chrominance divisors for quality = 0..100 (IJG standard tables) */
+static gint std_chrominance_sum[101] =
+{
+  G_MAXINT,
+  16320, 16320, 16320, 16218, 16010, 15731, 15523, 15369, 15245, 15110, 14985,
+  14864, 14754, 14635, 14526, 14429, 14346, 14267, 14204, 13790, 13121, 12511,
+  11954, 11453, 11010, 10567, 10175,  9787,  9455,  9122,  8844,  8565,  8288,
+   8114,  7841,  7616,  7447,  7227,  7060,  6897,  6672,  6562,  6396,  6226,
+   6116,  5948,  5838,  5729,  5614,  5505,  5396,  5281,  5172,  5062,  4947,
+   4837,  4726,  4614,  4506,  4395,  4282,  4173,  4061,  3950,  3839,  3727,
+   3617,  3505,  3394,  3284,  3169,  3060,  2949,  2836,  2780,  2669,  2556,
+   2445,  2336,  2221,  2111,  2000,  1888,  1778,  1666,  1555,  1444,  1332,
+   1223,  1110,   999,   891,   779,   668,   558,   443,   333,   224,   115,
+     64
+};
+
+/**
+ * jpeg_detect_quality:
+ * @cinfo: a pointer to a JPEG decompressor info.
+ *
+ * Returns the exact or estimated quality value that was used to save
+ * the JPEG image by analyzing the quantization table divisors.
+ *
+ * If an exact match for the IJG quantization tables is found, then a
+ * quality setting in the range 1..100 is returned.  If the quality
+ * can only be estimated, then a negative number in the range -1..-100
+ * is returned; its absolute value represents the maximum IJG quality
+ * setting to use.  If the quality cannot be reliably determined, then
+ * 0 is returned.
+ *
+ * This function must be called after jpeg_read_header() so that
+ * @cinfo contains the quantization tables read from the DQT markers
+ * in the file.
+ *
+ * Return Value: the JPEG quality setting in the range 1..100, -1..-100 or 0.
+ */
+gint
+jpeg_detect_quality (struct jpeg_decompress_struct *cinfo)
+{
+  gint t;
+  gint i;
+  gint sum[3];
+  gint q;
+
+  /* files using CMYK or having 4 quantization tables are unusual */
+  if (!cinfo || cinfo->output_components > 3 || cinfo->quant_tbl_ptrs[3])
+    return 0;
+
+  /* Most files use table 0 for luminance divisors (Y) and table 1 for
+   * chrominance divisors (Cb and Cr).  Some files use separate tables
+   * for Cb and Cr, so table 2 may also be used.
+   */
+  for (t = 0; t < 3; t++)
+    {
+      sum[t] = 0;
+      if (cinfo->quant_tbl_ptrs[t])
+        for (i = 0; i < DCTSIZE2; i++)
+          sum[t] += cinfo->quant_tbl_ptrs[t]->quantval[i];
+    }
+
+  if (cinfo->output_components > 1)
+    {
+      gint sums;
+
+      if (sum[0] < 64 || sum[1] < 64)
+        return 0;
+
+      /* compare with the chrominance table having the lowest sum */
+      if (sum[1] < sum[2] || sum[2] <= 0)
+        sums = sum[0] + sum[1];
+      else
+        sums = sum[0] + sum[2];
+
+      q = 100;
+      while (sums > std_luminance_sum[q] + std_chrominance_sum[q])
+        q--;
+
+      if (sum[0] == std_luminance_sum[q] && sum[1] == std_chrominance_sum[q])
+        return q;
+      else
+        return -q;
+    }
+  else
+    {
+      if (sum[0] < 64)
+        return 0;
+
+      q = 100;
+      while (sum[0] > std_luminance_sum[q])
+        q--;
+
+      if (sum[0] == std_luminance_sum[q])
+        return q;
+      else
+        return -q;
+    }
+}