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#include <mbgl/util/image.hpp>
#include <mbgl/util/char_array_buffer.hpp>
#include <istream>
#include <sstream>
#include <array>
extern "C"
{
#include <jpeglib.h>
}
namespace mbgl {
const static unsigned BUF_SIZE = 4096;
struct jpeg_stream_wrapper {
jpeg_source_mgr manager;
std::istream* stream;
std::array<JOCTET, BUF_SIZE> buffer;
};
static void init_source(j_decompress_ptr cinfo) {
jpeg_stream_wrapper* wrap = reinterpret_cast<jpeg_stream_wrapper*>(cinfo->src);
wrap->stream->seekg(0, std::ios_base::beg);
}
static boolean fill_input_buffer(j_decompress_ptr cinfo) {
jpeg_stream_wrapper* wrap = reinterpret_cast<jpeg_stream_wrapper*>(cinfo->src);
wrap->stream->read(reinterpret_cast<char*>(&wrap->buffer[0]), BUF_SIZE);
std::streamsize size = wrap->stream->gcount();
wrap->manager.next_input_byte = wrap->buffer.data();
wrap->manager.bytes_in_buffer = BUF_SIZE;
return (size > 0) ? TRUE : FALSE;
}
static void skip(j_decompress_ptr cinfo, long count) {
if (count <= 0) return; //A zero or negative skip count should be treated as a no-op.
jpeg_stream_wrapper* wrap = reinterpret_cast<jpeg_stream_wrapper*>(cinfo->src);
if (wrap->manager.bytes_in_buffer > 0 && count < static_cast<long>(wrap->manager.bytes_in_buffer))
{
wrap->manager.bytes_in_buffer -= count;
wrap->manager.next_input_byte = &wrap->buffer[BUF_SIZE - wrap->manager.bytes_in_buffer];
}
else
{
wrap->stream->seekg(count - wrap->manager.bytes_in_buffer, std::ios_base::cur);
// trigger buffer fill
wrap->manager.next_input_byte = nullptr;
wrap->manager.bytes_in_buffer = 0; //bytes_in_buffer may be zero on return.
}
}
static void term(j_decompress_ptr) {}
static void attach_stream(j_decompress_ptr cinfo, std::istream* in) {
if (cinfo->src == nullptr) {
cinfo->src = (struct jpeg_source_mgr *)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof(jpeg_stream_wrapper));
}
jpeg_stream_wrapper * src = reinterpret_cast<jpeg_stream_wrapper*> (cinfo->src);
src->manager.init_source = init_source;
src->manager.fill_input_buffer = fill_input_buffer;
src->manager.skip_input_data = skip;
src->manager.resync_to_restart = jpeg_resync_to_restart;
src->manager.term_source = term;
src->manager.bytes_in_buffer = 0;
src->manager.next_input_byte = nullptr;
src->stream = in;
}
static void on_error(j_common_ptr) {}
static void on_error_message(j_common_ptr cinfo) {
char buffer[JMSG_LENGTH_MAX];
(*cinfo->err->format_message)(cinfo, buffer);
throw std::runtime_error(std::string("JPEG Reader: libjpeg could not read image: ") + buffer);
}
struct jpeg_info_guard {
jpeg_info_guard(jpeg_decompress_struct* cinfo)
: i_(cinfo) {}
~jpeg_info_guard() {
jpeg_destroy_decompress(i_);
}
jpeg_decompress_struct* i_;
};
PremultipliedImage decodeJPEG(const uint8_t* data, size_t size) {
util::CharArrayBuffer dataBuffer { reinterpret_cast<const char*>(data), size };
std::istream stream(&dataBuffer);
jpeg_decompress_struct cinfo;
jpeg_info_guard iguard(&cinfo);
jpeg_error_mgr jerr;
cinfo.err = jpeg_std_error(&jerr);
jerr.error_exit = on_error;
jerr.output_message = on_error_message;
jpeg_create_decompress(&cinfo);
attach_stream(&cinfo, &stream);
int ret = jpeg_read_header(&cinfo, TRUE);
if (ret != JPEG_HEADER_OK)
throw std::runtime_error("JPEG Reader: failed to read header");
jpeg_start_decompress(&cinfo);
if (cinfo.out_color_space == JCS_UNKNOWN)
throw std::runtime_error("JPEG Reader: failed to read unknown color space");
if (cinfo.output_width == 0 || cinfo.output_height == 0)
throw std::runtime_error("JPEG Reader: failed to read image size");
size_t width = cinfo.output_width;
size_t height = cinfo.output_height;
size_t components = cinfo.output_components;
size_t rowStride = components * width;
PremultipliedImage image { width, height };
uint8_t* dst = image.data.get();
JSAMPARRAY buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr) &cinfo, JPOOL_IMAGE, rowStride, 1);
while (cinfo.output_scanline < cinfo.output_height) {
jpeg_read_scanlines(&cinfo, buffer, 1);
for (size_t i = 0; i < width; ++i) {
dst[0] = buffer[0][components * i];
dst[3] = 0xFF;
if (components > 2) {
dst[1] = buffer[0][components * i + 1];
dst[2] = buffer[0][components * i + 2];
} else {
dst[1] = dst[0];
dst[2] = dst[0];
}
dst += 4;
}
}
jpeg_finish_decompress(&cinfo);
return image;
}
} // namespace mbgl
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