TPNGImage help

Returns the current image color type.

property ColorType: Byte;

Description
Color type is the description for each pixel in the image. It's not recommended to change this property since it won't realloc data.

Color types	Description
COLOR_PALETTE	Each pixel is a palette index; a PLTE chunk must appear
COLOR_GRAYSCALE	Each pixel is a grayscale sample.
COLOR_RGB	Each pixel is an R,G,B triple.
COLOR_GRAYSCALEALPHA	Each pixel is a grayscale sample, followed by an alpha sample.
COLOR_RGBALPHA	Each pixel is an R,G,B triple, followed by an alpha sample.