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support writing rgb (no a) images with miniz - refs #1554

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This commit is contained in:
Dane Springmeyer 2012-11-06 09:19:40 -05:00
parent 5a99d7fbdb
commit cd3cc31752
2 changed files with 53 additions and 4 deletions
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3
include/mapnik/miniz_png.hpp
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@ -62,11 +62,12 @@ public:
void writetRNS(std::vector<unsigned> const& alpha);
template<typename T>
void writeIDAT(T const& image);
template<typename T>
void writeIDATStripAlpha(T const& image);
void writeIEND();
void toStream(std::ostream& stream);
private:
unsigned int flags;
tdefl_compressor *compressor;
tdefl_output_buffer *buffer;
static const unsigned char preamble[];

54
src/miniz_png.cpp
View File

@ -55,8 +55,7 @@ PNGWriter::PNGWriter(int level, int strategy)
{
throw std::runtime_error("compression level must be between 0 and 10");
}
flags = s_tdefl_num_probes[level]| (level <= 3) ? TDEFL_GREEDY_PARSING_FLAG : 0 | TDEFL_WRITE_ZLIB_HEADER;
mz_uint flags = s_tdefl_num_probes[level] | (level <= 3) ? TDEFL_GREEDY_PARSING_FLAG : 0 | TDEFL_WRITE_ZLIB_HEADER;
if (strategy == Z_FILTERED) flags |= TDEFL_FILTER_MATCHES;
else if (strategy == Z_HUFFMAN_ONLY) flags &= ~TDEFL_MAX_PROBES_MASK;
else if (strategy == Z_RLE) flags |= TDEFL_RLE_MATCHES;
@ -194,7 +193,10 @@ void PNGWriter::writePLTE(std::vector<rgb> const& palette)
void PNGWriter::writetRNS(std::vector<unsigned> const& alpha)
{
if (alpha.size() == 0) return;
if (alpha.size() == 0)
{
return;
}
std::vector<unsigned char> transparency(alpha.size());
unsigned char transparencySize = 0; // Stores position of biggest to nonopaque value.
@ -256,6 +258,50 @@ void PNGWriter::writeIDAT(T const& image)
finishChunk(IDAT);
}
template<typename T>
void PNGWriter::writeIDATStripAlpha(T const& image) {
// Write IDAT chunk.
size_t IDAT = startChunk(IDAT_tpl, 8);
mz_uint8 filter_type = 0;
tdefl_status status;
size_t stride = image.width() * 3;
size_t i, j;
mz_uint8 *scanline = (mz_uint8 *)MZ_MALLOC(stride);
for (unsigned int y = 0; y < image.height(); y++) {
// Write filter_type
status = tdefl_compress_buffer(compressor, &filter_type, 1, TDEFL_NO_FLUSH);
if (status != TDEFL_STATUS_OKAY)
{
MZ_FREE(scanline);
throw std::runtime_error("failed to compress image");
}
// Strip alpha bytes from scanline
mz_uint8 *row = (mz_uint8 *)image.getRow(y);
for (i = 0, j = 0; j < stride; i += 4, j += 3) {
scanline[j] = row[i];
scanline[j+1] = row[i+1];
scanline[j+2] = row[i+2];
}
// Write scanline
status = tdefl_compress_buffer(compressor, scanline, stride, TDEFL_NO_FLUSH);
if (status != TDEFL_STATUS_OKAY) {
MZ_FREE(scanline);
throw std::runtime_error("failed to compress image");
}
}
MZ_FREE(scanline);
status = tdefl_compress_buffer(compressor, NULL, 0, TDEFL_FINISH);
if (status != TDEFL_STATUS_DONE) throw std::runtime_error("failed to compress image");
finishChunk(IDAT);
}
void PNGWriter::writeIEND()
{
// Write IEND chunk.
@ -308,6 +354,8 @@ template void PNGWriter::writeIDAT<image_data_8>(image_data_8 const& image);
template void PNGWriter::writeIDAT<image_view<image_data_8> >(image_view<image_data_8> const& image);
template void PNGWriter::writeIDAT<image_data_32>(image_data_32 const& image);
template void PNGWriter::writeIDAT<image_view<image_data_32> >(image_view<image_data_32> const& image);
template void PNGWriter::writeIDATStripAlpha<image_data_32>(image_data_32 const& image);
template void PNGWriter::writeIDATStripAlpha<image_view<image_data_32> >(image_view<image_data_32> const& image);
}}