imagecolorallocate() returns a color identifier representing the color composed of the given RGB components. The image argument is the return from the imagecreate() function. red, green and blue are the values of the red, green and blue component of the requested color respectively. These parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF. imagecolorallocate() must be called to create each color that is to be used in the image represented by image.
Nota: The first call to imagecolorallocate() fills the background color.
Returns -1 if the allocation failed.