Image ImageFormat_JPEG::decode(IReader& reader) const
{
const int64 size = reader.size();
uint8* buffer = static_cast<uint8*>(::malloc(static_cast<size_t>(size)));
reader.read(buffer, size);
int width, height;
tjhandle tj = ::tjInitDecompress();
::tjDecompressHeader(tj, buffer, static_cast<unsigned long>(size), &width, &height);
Image image(width, height);
::tjDecompress(
tj,
buffer,
static_cast<unsigned long>(size),
image.dataAsUint8(),
image.width(),
image.stride(),
image.height(),
sizeof(Color),
0);
::tjDestroy(tj);
::free(buffer);
return image;
}
Size ImageFormat_JPEG::getSize(const IReader& reader) const
{
uint8 buf[24];
if (!reader.lookahead(buf))
{
return{ 0, 0 };
}
const auto len = reader.size();
//
// http://www.wischik.com/lu/programmer/get-image-size.html
//
if ((buf[0] == 0xFF && buf[1] == 0xD8 && buf[2] == 0xFF && buf[3] == 0xE0 && buf[6] == 'J' && buf[7] == 'F' && buf[8] == 'I' && buf[9] == 'F')
|| (buf[0] == 0xFF && buf[1] == 0xD8 && buf[2] == 0xFF && buf[3] == 0xE1 && buf[6] == 'E' && buf[7] == 'x' && buf[8] == 'i' && buf[9] == 'f'))
{
int64 pos = 2;
while (buf[2] == 0xFF)
{
if (buf[3] == 0xC0
|| buf[3] == 0xC1
|| buf[3] == 0xC2
|| buf[3] == 0xC3
|| buf[3] == 0xC5
|| buf[3] == 0xC6
|| buf[3] == 0xC7
|| buf[3] == 0xC9
|| buf[3] == 0xCA
|| buf[3] == 0xCB
|| buf[3] == 0xCD
|| buf[3] == 0xCE
|| buf[3] == 0xCF)
{
break;
}
pos += 2 + (buf[4] << 8) + buf[5];
if (pos + 12 > len)
{
break;
}
reader.lookahead(buf + 2, pos, 12);
}
}
// JPEG: (first two bytes of buf are first two bytes of the jpeg file; rest of buf is the DCT frame
if (buf[0] == 0xFF && buf[1] == 0xD8 && buf[2] == 0xFF)
{
const int32 width = (buf[9] << 8) + buf[10];
const int32 height = (buf[7] << 8) + buf[8];
return{ width, height };
}
return{ 0, 0 };
}
TemporaryFile(const IReader& reader)
: m_path(FileSystem::UniqueFilePath())
{
WritableMemoryMapping file(m_path);
const size_t size = static_cast<size_t>(reader.size());
file.map(0, size);
reader.lookahead(file.data(), size);
file.unmap();
}
