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