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