sij/mapnik
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Support more compact encodings for images that don't have all that many colors. (blank, solid, etc)

Browse source
This commit is contained in:
Daniel Patterson 2015-05-16 10:10:32 -07:00
parent dd4b84bd08
commit 6bcae9db9c
1 changed files with 38 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

44
include/mapnik/png_io.hpp
View file

@ -741,12 +741,11 @@ void save_as_png8_libimagequant(T1 & file,
liq_image *liq_image = liq_image_create_rgba_rows(attr, (void **)buf, width, height, 0);
liq_result *res = liq_quantize_image(attr, liq_image);
// Store palettized version
if (opts.iq_dither != -1) {
liq_set_dithering_level(res, opts.iq_dither);
}
image_gray8 reduced_image(width, height);
liq_write_remapped_image(res, liq_image, (void *)reduced_image.data(), width*height*sizeof(gray8_t));
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);
std::vector<mapnik::rgb> palette;
@ -758,9 +757,42 @@ void save_as_png8_libimagequant(T1 & file,
alpha.push_back(liq_pal->entries[i].a);
}
// TODO: support 1 & 4 bit packing, not just 8, to reduce the file size, particularly on blank
// or solid tiles
save_as_png(file, palette, reduced_image, width, height, 8, alpha, opts);
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);
for (unsigned y = 0; y < height; ++y)
{
mapnik::image_rgba8::pixel_type const * row = image.get_row(y);
mapnik::image_gray8::pixel_type * row_out = reduced_image.get_row(y);
byte index = 0;
for (unsigned x = 0; x < width; ++x)
{
index = row[x];
if (x%2 == 0)
{
index = index<<4;
}
row_out[x>>1] |= index;
}
}
save_as_png(file, palette, reduced_image, width, height, 4, alpha, opts);
}
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);
reduced_image.set(0);
save_as_png(file, palette, reduced_image, width, height, 1, alpha, opts);
}
liq_attr_destroy(attr);
liq_image_destroy(liq_image);