82 lines
3.1 KiB
C++
82 lines
3.1 KiB
C++
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#include "sample_decoder.hpp"
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#include <algorithm>
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namespace pdfengine {
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std::vector<uint8_t> SampleDecoder::unpackSamples(const std::vector<uint8_t>& rawBytes,
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int width,
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int height,
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int components,
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int bitsPerComponent) {
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if (rawBytes.empty() || width <= 0 || height <= 0 || components <= 0) {
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return {};
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}
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if (bitsPerComponent == 8) {
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return rawBytes;
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}
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const size_t expectedSamples = static_cast<size_t>(width) * height * components;
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std::vector<uint8_t> unpacked;
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unpacked.reserve(expectedSamples);
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if (bitsPerComponent == 1) {
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for (int y = 0; y < height; ++y) {
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int samplesInRow = width * components;
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int bytesInRow = (samplesInRow + 7) / 8;
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size_t rowOffset = static_cast<size_t>(y) * bytesInRow;
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if (rowOffset >= rawBytes.size()) break;
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for (int s = 0; s < samplesInRow; ++s) {
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size_t byteIdx = rowOffset + (s / 8);
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if (byteIdx >= rawBytes.size()) break;
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uint8_t b = rawBytes[byteIdx];
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uint8_t bit = (b >> (7 - (s % 8))) & 1;
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unpacked.push_back(bit ? 255 : 0);
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}
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}
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} else if (bitsPerComponent == 2) {
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for (int y = 0; y < height; ++y) {
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int samplesInRow = width * components;
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int bytesInRow = (samplesInRow + 3) / 4;
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size_t rowOffset = static_cast<size_t>(y) * bytesInRow;
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if (rowOffset >= rawBytes.size()) break;
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for (int s = 0; s < samplesInRow; ++s) {
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size_t byteIdx = rowOffset + (s / 4);
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if (byteIdx >= rawBytes.size()) break;
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uint8_t b = rawBytes[byteIdx];
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uint8_t val = (b >> (6 - 2 * (s % 4))) & 0x03;
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unpacked.push_back(static_cast<uint8_t>(val * 85)); // 0x03 -> 255
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}
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}
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} else if (bitsPerComponent == 4) {
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for (int y = 0; y < height; ++y) {
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int samplesInRow = width * components;
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int bytesInRow = (samplesInRow + 1) / 2;
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size_t rowOffset = static_cast<size_t>(y) * bytesInRow;
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if (rowOffset >= rawBytes.size()) break;
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for (int s = 0; s < samplesInRow; ++s) {
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size_t byteIdx = rowOffset + (s / 2);
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if (byteIdx >= rawBytes.size()) break;
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uint8_t b = rawBytes[byteIdx];
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uint8_t val = (s % 2 == 0) ? ((b >> 4) & 0x0F) : (b & 0x0F);
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unpacked.push_back(static_cast<uint8_t>(val * 17)); // 0x0F -> 255
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}
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}
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} else if (bitsPerComponent == 16) {
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// Take upper 8 bits of each 16-bit sample
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for (size_t i = 0; i + 1 < rawBytes.size() && unpacked.size() < expectedSamples; i += 2) {
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unpacked.push_back(rawBytes[i]);
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}
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} else {
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// Fallback pass-through
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return rawBytes;
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}
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return unpacked;
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}
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} // namespace pdfengine
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