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Support reading grayscale pngs

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This commit is contained in:
Nikita Lisitsa 2021-02-27 19:44:17 +03:00
parent 12e2bff790
commit 6661299573
2 changed files with 25 additions and 10 deletions
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1
libs/gfx/include/psemek/gfx/pixmap.hpp
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@ -24,5 +24,6 @@ namespace psemek::gfx
void write_ppm(pixmap_rgb const & p, std::ostream & os);
pixmap_rgba read_png(std::istream & is);
pixmap_monochrome read_png_monochrome(std::istream & is);
}

34
libs/gfx/source/png.cpp
View file

@ -3,14 +3,13 @@
#include <psemek/log/log.hpp>
#include <psemek/util/at_scope_exit.hpp>
#include <vector>
#include <png.h>
namespace psemek::gfx
{
pixmap_rgba read_png(std::istream & is)
template <typename Pixel>
basic_pixmap<Pixel> read_png_impl(std::istream & is, png_byte expected_color_type)
{
png_error_ptr error = [](png_structp, png_const_charp str)
{
@ -52,17 +51,22 @@ namespace psemek::gfx
auto const color_type = png_get_color_type(png, info);
auto const bit_depth = png_get_bit_depth(png, info);
if (color_type != PNG_COLOR_TYPE_RGBA)
throw std::runtime_error("PNG color types other than RGBA are not supported");
if (color_type != expected_color_type)
throw std::runtime_error("PNG color type not supported");
if (bit_depth != 8)
throw std::runtime_error("PNG bit depths other than 8 are not supported");
if (bit_depth == 16)
png_set_strip_16(png);
pixmap_rgba result({width, height});
if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
png_set_expand_gray_1_2_4_to_8(png);
png_read_update_info(png, info);
basic_pixmap<Pixel> result({width, height});
auto const row_bytes = png_get_rowbytes(png, info);
if (row_bytes != width * 4)
throw std::runtime_error("PNG row bytes is wrong");
if (row_bytes != width * sizeof(Pixel))
throw std::runtime_error("PNG row bytes mismatch");
for (std::uint32_t i = 0; i < height; ++i)
png_read_row(png, reinterpret_cast<png_bytep>(result.data() + i * width), nullptr);
@ -70,4 +74,14 @@ namespace psemek::gfx
return result;
}
pixmap_rgba read_png(std::istream & is)
{
return read_png_impl<color_rgba>(is, PNG_COLOR_TYPE_RGBA);
}
pixmap_monochrome read_png_monochrome(std::istream & is)
{
return read_png_impl<std::uint8_t>(is, PNG_COLOR_TYPE_GRAY);
}
}