accessing the pixels' alpha values within a script (the "a" of rgba) when scanning a layer

hi all,

I need to evaluate/scan all pixels of a given PSD layer via a script. for accessing the R, G, B values I

seached the script reference and found the RGBColor element as

Properties

Property Value type What it is

blue number [0..255] Read-write. The blue color value (default: 255).

green number [0..255] Read-write. The green color value (default: 255)

hexValue string Read-write. The hexadecimal representation of the color.

red number [0..255] Read-write. The red color value (default: 255)

typename string Read-only. The class name of the referenced RGBColor object.

BUT I NEED to evaluate the alpha value of the layer's pixels. where is this value stored?

is it mathematically imbedded in R, G and B?

does anybody has a sample for accessing all pixels of a layer?

thanks for any info and link to a sample script, or any note.

best

stephen