Scripting Magic Wand selection by preset color

[King-Ki5EBD]

Hello,

I'm trying to write a script to use the magic wand to select a specific color and contract the selection by 3 pixels. However, the magic wand script requires identify the location of a pixel which doesn't work for me because the location of the specific color changes from image to image. Is there any way to get around this?

function magicWand(x,y,t,a,c,s) {
    if(arguments.length < 2) return;// make sure have x,y
    if(undefined == t) var t = 32;// set defaults of optional arguments
    if(undefined == a) var a = true;
    if(undefined == c) var c = false;
     if(undefined == s) var s = false;
    var desc = new ActionDescriptor();
        var ref = new ActionReference();
        ref.putProperty( charIDToTypeID('Chnl'), charIDToTypeID('fsel') );
    desc.putReference( charIDToTypeID('null'), ref );
        var positionDesc = new ActionDescriptor();
        positionDesc.putUnitDouble( charIDToTypeID('Hrzn'), charIDToTypeID('#Rlt'), x );// in pixels
        positionDesc.putUnitDouble( charIDToTypeID('Vrtc'), charIDToTypeID('#Rlt'), y );
    desc.putObject( charIDToTypeID('T   '), charIDToTypeID('Pnt '), positionDesc );
    desc.putInteger( charIDToTypeID('Tlrn'), t);// tolerance
    desc.putBoolean( charIDToTypeID('Mrgd'), s );// sample all layers
    if(!c) desc.putBoolean( charIDToTypeID( "Cntg" ), false );//  contiguous
    desc.putBoolean( charIDToTypeID('AntA'), a );// anti-alias
    executeAction( charIDToTypeID('setd'), desc, DialogModes.NO );
};

[JJMack]

If you kown the color use color range instead of the magic wand. get its lab valuse.

function colorRange(fuzziness, luminance, a, b, luminance2, a2, b2, colorModel) {
	var descriptor = new ActionDescriptor();
	var descriptor2 = new ActionDescriptor();
	var descriptor3 = new ActionDescriptor();
	descriptor.putInteger( stringIDToTypeID( "fuzziness" ), fuzziness );
	descriptor2.putDouble( stringIDToTypeID( "luminance" ), luminance );
	descriptor2.putDouble( stringIDToTypeID( "a" ), a );
	descriptor2.putDouble( stringIDToTypeID( "b" ), b );
	descriptor.putObject( stringIDToTypeID( "minimum" ), stringIDToTypeID( "labColor" ), descriptor2 );
	descriptor3.putDouble( stringIDToTypeID( "luminance" ), luminance2 );
	descriptor3.putDouble( stringIDToTypeID( "a" ), a2 );
	descriptor3.putDouble( stringIDToTypeID( "b" ), b2 );
	descriptor.putObject( charIDToTypeID( "Mxm " ), stringIDToTypeID( "labColor" ), descriptor3 );
	descriptor.putInteger( stringIDToTypeID( "colorModel" ), colorModel );
	executeAction( stringIDToTypeID( "colorRange" ), descriptor, DialogModes.NO );
}

[r-bin · Accepted solution]

You can add an empty layer,

draw a pixel of the desired color in it at position (0,0),

move the layer to position (-1, -1),

apply magicWand (-1, -1),

delete the temporary layer.

[King-Ki5EBD]

I had trouble with finding the right command to add a layer. So I recorded the original color of a pixel in coordinate (0,0), colored pixel in (0,0), and used magic wand on pixel (0,0). When I was done with the pixel, I colored it back to the original color. 

[Kukurykus]

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