The cairo-format-t enumeration is used to identify the memory format of image data.

New entries may be added in future versions.

(defcenum cairo-format-t
  (:invalid -1)
  (:argb32 0)
  (:rgb24 1)
  (:a8 2)
  (:a1 3)
  (:rgb16-565 4)
  (:rgb30 5))  

:invalid

No such format exists or is supported.

: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.

: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.

:a8

Each pixel is a 8-bit quantity holding an alpha value.

: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.

: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.

:rgb30

Like :rgb24 but with 10 bpc.