Question

i want to make a little photoshop javascript. Technically, i just need to know how to compare the color values of pixels af if they were an array with three integer values in each, for example: (pseudocode)

for all pixels x
    for all pixels y
        if left pixel's green channel is bigger than red channel:
            set the blue channel to 25
        else
            if the blue channel is greater than 50
                set the green channel to 0

in the documentation, there’s a ton of things like filters, text and layers you can do, but how do you do something as simple as this?

Answer 1

Reading and writing pixel values in Photoshop scripts is indeed not as simple as it could be … Check out the following script which inverts the blue channel of an image:

var doc = app.open(new File("~/Desktop/test1.bmp"));

var sampler = doc.colorSamplers.add([0, 0]);

for (var x = 0; x < doc.width; ++x) {
    for (var y = 0; y < doc.height; ++y) {        

        sampler.move([x, y]);
        var color = sampler.color;

        var region = [
            [x, y],
            [x + 1, y],
            [x + 1, y + 1],
            [x, y + 1],
            [x, y]
        ];

        var newColor = new SolidColor();
        newColor.rgb.red = color.rgb.red;
        newColor.rgb.green = 255 - color.rgb.green;
        newColor.rgb.blue = color.rgb.blue;

        doc.selection.select(region);
        doc.selection.fill(newColor);

    }
}

I’m not sure if there’s a prettier way of setting a pixel color than the select + fill trick.

This script runs super slow, so maybe Photoshop scripts are not the best tool for pixel manipulation …