cairo_format_t is used to identify the memory format of image data. New entries may be added in future versions. CAIRO_FORMAT_INVALID no such format exists or is supported. CAIRO_FORMAT_ARGB32 each pixel is a 32-bit quantity, with alpha in the upper 8 bits, then red, then green, then blue. The 32-bit quantities are stored native-endian. Pre-multiplied alpha is used. (That is, 50% transparent red is 0x80800000, not 0x80ff0000.) (Since 1.0) CAIRO_FORMAT_RGB24 each pixel is a 32-bit quantity, with the upper 8 bits unused. Red, Green, and Blue are stored in the remaining 24 bits in that order. (Since 1.0) CAIRO_FORMAT_A8 each pixel is a 8-bit quantity holding an alpha value. (Since 1.0) CAIRO_FORMAT_A1 each pixel is a 1-bit quantity holding an alpha value. Pixels are packed together into 32-bit quantities. The ordering of the bits matches the endianess of the platform. On a big-endian machine, the first pixel is in the uppermost bit, on a little-endian machine the first pixel is in the least-significant bit. (Since 1.0) CAIRO_FORMAT_RGB16_565 each pixel is a 16-bit quantity with red in the upper 5 bits, then green in the middle 6 bits, and blue in the lower 5 bits. (Since 1.2) CAIRO_FORMAT_RGB30 like RGB24 but with 10bpc. (Since 1.12) Since 1.0