cmpSize

Declaration

var cmpSize: Int16

Discussion

Color QuickDraw expects that the sizes of all components are the same, and that the value of the cmpCount field multiplied by the value of the cmpSize field is less than or equal to the value in the pixelSize field.For an indexed pixel value, which has only one component, the value of the cmpSize field is the same as the value of the pixelSize field; that is, 1, 2, 4, or 8. For direct pixels there are two additional possibilities. A 16-bit pixel, which has three components, has a cmpSize value of 5; this leaves an unused high-order bit, which Color QuickDraw sets to 0. A 32-bit pixel, which has three components (red, green, and blue), has a cmpSize value of 8; this leaves an unused high-order byte, which Color QuickDraw sets to 0.

If presented with a 32-bit image (for example, in the CopyBits procedure) Color QuickDraw passes whatever bits are there, and it does not set the high byte to 0. Generally, therefore, your application should clear the memory for the image to 0 before creating a 16-bit or 32-bit image.