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Enable support for output palette gamma correction using libimagequant.

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This commit is contained in:
Daniel Patterson 2015-05-16 13:33:08 -07:00
parent bf354eeded
commit 10553e0793
1 changed files with 17 additions and 11 deletions
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28
include/mapnik/png_io.hpp
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@ -41,7 +41,6 @@
extern "C"
{
#include <png.h>
// TODO: make this optional
#include <libimagequant.h>
}
@ -724,46 +723,53 @@ void save_as_png8_libimagequant(T1 & file,
unsigned width = image.width();
unsigned height = image.height();
// TODO: can this be done as a single blob, rather than using rows?
uint32_t *buf[height];
// TODO: this won't work on big-endian architectures, liq expects
// data in RGBA byte order
// TODO: this won't work on big-endian architectures, liq expects data in RGBA byte order
for (size_t y = 0; y < height; ++y)
{
buf[y] = (uint32_t *)image.get_row(y);
}
// Set up libimagequant
liq_attr *attr = liq_attr_create();
// TODO: set gamma
// TODO: error checking
liq_set_speed(attr, opts.iq_speed);
liq_image *liq_image = liq_image_create_rgba_rows(attr, (void **)buf, width, height, 0);
// Do the quantization
liq_result *res = liq_quantize_image(attr, liq_image);
if (opts.iq_dither != -1) {
if (opts.iq_dither != -1)
{
liq_set_dithering_level(res, opts.iq_dither);
}
if (opts.gamma > 0)
{
liq_set_output_gamma(res, opts.gamma);
}
// Extract the generated 8-bit imag
image_gray8 quantized_image(width, height);
liq_write_remapped_image(res, liq_image, (void *)quantized_image.data(), width*height*sizeof(gray8_t));
const liq_palette *liq_pal = liq_get_palette(res);
// Extract the generated palette and alpha vector from libimagequant
std::vector<mapnik::rgb> palette;
std::vector<unsigned> alpha;
const liq_palette *liq_pal = liq_get_palette(res);
for (int i = 0; i < liq_pal->count; ++i)
{
palette.push_back({ liq_pal->entries[i].r, liq_pal->entries[i].g, liq_pal->entries[i].b });
alpha.push_back(liq_pal->entries[i].a);
}
// Encode the image, using a bit-depth depending on the number of colors in the generated
// palette
if (palette.size() > 16) // 8-bit encoding
{
save_as_png(file, palette, quantized_image, width, height, 8, alpha, opts);
}
else if (palette.size() > 1) // up to 16 colors, 4-bit encoding
{
// <=16 colors -> write 4-bit color depth PNG
unsigned image_width = ((width + 7) >> 1) & ~3U; // 4-bit image, round up to 32-bit boundary
unsigned image_height = height;
image_gray8 reduced_image(image_width, image_height);
@ -786,7 +792,6 @@ void save_as_png8_libimagequant(T1 & file,
}
else // 1 color, 1-bit encoding
{
// 1 color image -> write 1-bit color depth PNG
unsigned image_width = ((width + 15) >> 3) & ~1U; // 1-bit image, round up to 16-bit boundary
unsigned image_height = height;
image_gray8 reduced_image(image_width, image_height);
@ -794,6 +799,7 @@ void save_as_png8_libimagequant(T1 & file,
save_as_png(file, palette, reduced_image, width, height, 1, alpha, opts);
}
// Cleanup libimagequant
liq_attr_destroy(attr);
liq_image_destroy(liq_image);
liq_result_destroy(res);