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#include <mbgl/util/image.hpp>
#include <mbgl/util/premultiply.hpp>
#include <mbgl/util/char_array_buffer.hpp>
#include <mbgl/platform/log.hpp>
#include <istream>
#include <sstream>
extern "C"
{
#include <png.h>
}
namespace mbgl {
static void user_error_fn(png_structp, png_const_charp error_msg) {
throw std::runtime_error(std::string("failed to read invalid png: '") + error_msg + "'");
}
static void user_warning_fn(png_structp, png_const_charp warning_msg) {
Log::Warning(Event::Image, "ImageReader (PNG): %s", warning_msg);
}
static void png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) {
std::istream* fin = reinterpret_cast<std::istream*>(png_get_io_ptr(png_ptr));
fin->read(reinterpret_cast<char*>(data), length);
std::streamsize read_count = fin->gcount();
if (read_count < 0 || static_cast<png_size_t>(read_count) != length)
{
png_error(png_ptr, "Read Error");
}
}
struct png_struct_guard {
png_struct_guard(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)
: p_(png_ptr_ptr),
i_(info_ptr_ptr) {}
~png_struct_guard() {
png_destroy_read_struct(p_,i_,nullptr);
}
png_structpp p_;
png_infopp i_;
};
PremultipliedImage decodePNG(const uint8_t* data, size_t size) {
util::CharArrayBuffer dataBuffer { reinterpret_cast<const char*>(data), size };
std::istream stream(&dataBuffer);
png_byte header[8] = { 0 };
stream.read(reinterpret_cast<char*>(header), 8);
if (stream.gcount() != 8)
throw std::runtime_error("PNG reader: Could not read image");
int is_png = !png_sig_cmp(header, 0, 8);
if (!is_png)
throw std::runtime_error("File or stream is not a png");
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
if (!png_ptr)
throw std::runtime_error("failed to allocate png_ptr");
// catch errors in a custom way to avoid the need for setjmp
png_set_error_fn(png_ptr, png_get_error_ptr(png_ptr), user_error_fn, user_warning_fn);
png_infop info_ptr;
png_struct_guard sguard(&png_ptr, &info_ptr);
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
throw std::runtime_error("failed to create info_ptr");
png_set_read_fn(png_ptr, &stream, png_read_data);
png_set_sig_bytes(png_ptr, 8);
png_read_info(png_ptr, info_ptr);
png_uint_32 width = 0;
png_uint_32 height = 0;
int bit_depth = 0;
int color_type = 0;
png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, nullptr, nullptr, nullptr);
UnassociatedImage image { width, height };
if (color_type == PNG_COLOR_TYPE_PALETTE)
png_set_expand(png_ptr);
if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
png_set_expand(png_ptr);
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
png_set_expand(png_ptr);
if (bit_depth == 16)
png_set_strip_16(png_ptr);
if (color_type == PNG_COLOR_TYPE_GRAY ||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
png_set_gray_to_rgb(png_ptr);
png_set_add_alpha(png_ptr, 0xff, PNG_FILLER_AFTER);
if (png_get_interlace_type(png_ptr,info_ptr) == PNG_INTERLACE_ADAM7) {
png_set_interlace_handling(png_ptr); // FIXME: libpng bug?
// according to docs png_read_image
// "..automatically handles interlacing,
// so you don't need to call png_set_interlace_handling()"
}
png_read_update_info(png_ptr, info_ptr);
// we can read whole image at once
// alloc row pointers
const std::unique_ptr<png_bytep[]> rows(new png_bytep[height]);
for (unsigned row = 0; row < height; ++row)
rows[row] = image.data.get() + row * width * 4;
png_read_image(png_ptr, rows.get());
png_read_end(png_ptr, nullptr);
return util::premultiply(std::move(image));
}
} // namespace mbgl
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