Selecting pixels in a picture and changing their color with a script

Question

Hi, I'm brand new to photoshop scripting, and I want to make a script that takes every pixel of a color and replaces it with a new color,
I'm having the hardest time finding any information on the internet on how to do it though.
I do have some background in other coding, so the concepts are not new, just the language and functions.
I know there's tools and filters already, but I want to make a script so I can add features.
Any help would be appreciated.
Thank you!
(P.S. Is there a way to open and read code of a pre-exsisting filter, or is that impossible?)

Answer 1

To create your own filters you would need to download the SDK I think you might find an example of a filter.
With Photoshop this might be close...
main();
function main(){
if(!documents.length) return;
var sColour =new SolidColor;
sColour.rgb.hexValue ='245887';
selectColorRange(0,sColour);
try{
var SB = activeDocument.selection.bounds;
    }catch(e){return;}
var FillColour =new SolidColor;
FillColour.rgb.hexValue = 'ff0000';
activeDocument.selection.fill(FillColour,ColorBlendMode.NORMAL);
activeDocument.selection.deselect();
function selectColorRange( fuzz, solidColor){
var scaleA = (solidColor.lab.a + 128.5) / 256;
    var desc11 = new ActionDescriptor();
    desc11.putInteger( charIDToTypeID( "Fzns" ), fuzz );
        var desc12 = new ActionDescriptor();
        desc12.putDouble( charIDToTypeID( "Lmnc" ), solidColor.lab.l );
        desc12.putDouble( charIDToTypeID( "A   " ), solidColor.lab.a + scaleA);
        desc12.putDouble( charIDToTypeID( "B   " ), solidColor.lab.b + scaleA);
    desc11.putObject( charIDToTypeID( "Mnm " ), charIDToTypeID( "LbCl"), desc12 );
    desc11.putObject( charIDToTypeID( "Mxm " ), charIDToTypeID( "LbCl" ), desc12 );
executeAction( charIDToTypeID( "ClrR" ), desc11, DialogModes.NO );
Using Christophs suggestion...
//Use 1 pixel to colour
app.activeDocument.colorSamplers.removeAll();
var mySampler = app.activeDocument.colorSamplers.add([new UnitValue(1,'px'),new UnitValue(1,'px' )]);
//Get original colour
var oColour = new SolidColor();
oColour = mySampler.color;
app.activeDocument.colorSamplers.removeAll();
//Select colour
var sColour = new SolidColor();
sColour.rgb.hexValue ='31618f';
activeDocument.selection.select([[0,0],[1,0],[1,1],[0,1]], SelectionType.REPLACE, 0, false);
activeDocument.selection.fill(sColour,ColorBlendMode.NORMAL);
//Replacement Colour
var rColour = new SolidColor();
rColour.rgb.hexValue ='ff0000';
activeDocument.selection.similar(0, false);
activeDocument.selection.fill(rColour,ColorBlendMode.NORMAL);
activeDocument.selection.deselect();
//Replace original colour.
activeDocument.selection.select([[0,0],[1,0],[1,1],[0,1]], SelectionType.REPLACE, 0, false);
activeDocument.selection.fill(oColour,ColorBlendMode.NORMAL);
activeDocument.selection.deselect();