An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
Value of red component
Value of green component
Value of blue component
A value between
0 indicates completely opaque while
127 indicates completely transparent.
The colors parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.
Returns the index of the specified color+alpha in the palette of the image, or -1 if the color does not exist in the image's palette.