ofxLayerMask

This addon makes it easy to draw a graphical layer, and then hide parts of that layer with a mask. It operates on the same principles as layer masking in Photoshop.

Under the hood it uses frame buffer objects and shaders - but the addon handles all of that for you and lets you focus on drawing.

How to get started

If you clone this repo to your addon directory and run the simple example, you will see something like this:

The code follows this simple pattern. Just go ahead and draw whatever you like in the layer and the mask:

ofxLayerMask masker;

void ofApp::setup() {
    masker.setup(width, height);
    masker.newLayer();
}

void ofApp::update(){
    //Draw any background here

    masker.beginMask();
    //Draw any mask you like
    masker.endMask();
    
    masker.beginLayer();
    //Draw any layer you like
    masker.endLayer();
}

void ofApp::draw() {
    masker.draw();
}

Working with multiple layers

You can add as many layers as you like. If you run the multi example you will see something like this:

The pattern is very similar, with just a couple of differences:

ofxLayerMask masker;
int layer1, layer2;

void ofApp::setup() {
    masker.setup(width, height);
    layer1 = masker.newLayer();
    layer2 = masker.newLayer();
}

void ofApp::update(){
    //Draw any background here

    masker.beginMask(layer1);
    //Draw any mask you like
    masker.endMask(layer1);
    
    masker.beginLayer(layer1);
    //Draw any layer you like
    masker.endLayer(layer1);

    masker.beginMask(layer2);
    //Draw any mask you like
    masker.endMask(layer2);
    
    masker.beginLayer(layer2);
    //Draw any layer you like
    masker.endLayer(layer2);
}

void ofApp::draw() {
    masker.draw();
}

Using the overlay

When you start working with multiple masks and layers it can quickly become confusing without visual feedback. While the examples are running, hit 'o' to get an overlay like this:

To toggle the overlay in your own code, call the toggleOverlay() function:

void ofApp::keyPressed(int key){
    if(key == 'o') {
        masker.toggleOverlay();
    }
}

Dependencies

The addon has no dependencies. Tested against openFrameworks 0.10.1.