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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "lib/extras/common.h"
#include <jxl/codestream_header.h>
#include <jxl/types.h>
#include <cstddef>
#include <vector>
#include "lib/extras/packed_image.h"
#include "lib/jxl/base/printf_macros.h"
#include "lib/jxl/base/status.h"
namespace jxl {
namespace extras {
Status SelectFormat(const std::vector<JxlPixelFormat>& accepted_formats,
const JxlBasicInfo& basic_info, JxlPixelFormat* format) {
const size_t original_bit_depth = basic_info.bits_per_sample;
size_t current_bit_depth = 0;
size_t num_alpha_channels = (basic_info.alpha_bits != 0 ? 1 : 0);
size_t num_channels = basic_info.num_color_channels + num_alpha_channels;
for (;;) {
for (const JxlPixelFormat& candidate : accepted_formats) {
if (candidate.num_channels != num_channels) continue;
const size_t candidate_bit_depth =
PackedImage::BitsPerChannel(candidate.data_type);
if (
// Candidate bit depth is less than what we have and still enough
(original_bit_depth <= candidate_bit_depth &&
candidate_bit_depth < current_bit_depth) ||
// Or larger than the too-small bit depth we currently have
(current_bit_depth < candidate_bit_depth &&
current_bit_depth < original_bit_depth)) {
*format = candidate;
current_bit_depth = candidate_bit_depth;
}
}
if (current_bit_depth == 0) {
if (num_channels > basic_info.num_color_channels) {
// Try dropping the alpha channel.
--num_channels;
continue;
}
return JXL_FAILURE("no appropriate format found");
}
break;
}
if (current_bit_depth < original_bit_depth) {
JXL_WARNING("encoding %" PRIuS "-bit original to %" PRIuS " bits",
original_bit_depth, current_bit_depth);
}
return true;
}
} // namespace extras
} // namespace jxl
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