Docs 0.11.0

#include "ofApp.h"

//--------------------------------------------------------------
void ofApp::setup(){
    ofEnableAlphaBlending();
    
    srcImg.load("A.jpg");
    dstImg.load("B.jpg");
    brushImg.load("brush.png");
    
    int width = srcImg.getWidth();
    int height = srcImg.getHeight();
    
    maskFbo.allocate(width,height);
    fbo.allocate(width,height);
    
    // There are 3 of ways of loading a shader:
    //
    //  1 - Using just the name of the shader and ledding ofShader look for .frag and .vert: 
    //      Ex.: shader.load( "myShader");
    //
    //  2 - Giving the right file names for each one: 
    //      Ex.: shader.load( "myShader.vert","myShader.frag");
    //
    //  3 - And the third one it�s passing the shader programa on a single string;
    //


    #ifdef TARGET_OPENGLES
    shader.load("shaders_gles/alphamask.vert","shaders_gles/alphamask.frag");
    #else
    if(ofIsGLProgrammableRenderer()){
    	string vertex = "#version 150\n\
    	\n\
		uniform mat4 projectionMatrix;\n\
		uniform mat4 modelViewMatrix;\n\
    	uniform mat4 modelViewProjectionMatrix;\n\
    	\n\
    	\n\
    	in vec4  position;\n\
    	in vec2  texcoord;\n\
    	\n\
    	out vec2 texCoordVarying;\n\
    	\n\
    	void main()\n\
    	{\n\
	        texCoordVarying = texcoord;\
    		gl_Position = modelViewProjectionMatrix * position;\n\
    	}";
		string fragment = "#version 150\n\
		\n\
		uniform sampler2DRect tex0;\
		uniform sampler2DRect maskTex;\
        in vec2 texCoordVarying;\n\
		\
        out vec4 fragColor;\n\
		void main (void){\
		vec2 pos = texCoordVarying;\
		\
		vec3 src = texture(tex0, pos).rgb;\
		float mask = texture(maskTex, pos).r;\
		\
		fragColor = vec4( src , mask);\
		}";
		shader.setupShaderFromSource(GL_VERTEX_SHADER, vertex);
		shader.setupShaderFromSource(GL_FRAGMENT_SHADER, fragment);
		shader.bindDefaults();
		shader.linkProgram();
    }else{
		string shaderProgram = "#version 120\n \
		#extension GL_ARB_texture_rectangle : enable\n \
		\
		uniform sampler2DRect tex0;\
		uniform sampler2DRect maskTex;\
		\
		void main (void){\
		vec2 pos = gl_TexCoord[0].st;\
		\
		vec3 src = texture2DRect(tex0, pos).rgb;\
		float mask = texture2DRect(maskTex, pos).r;\
		\
		gl_FragColor = vec4( src , mask);\
		}";
		shader.setupShaderFromSource(GL_FRAGMENT_SHADER, shaderProgram);
		shader.linkProgram();
    }
    #endif

    // Let�s clear the FBO�s
    // otherwise it will bring some junk with it from the memory    
    maskFbo.begin();
    ofClear(0,0,0,255);
    maskFbo.end();
    
    fbo.begin();
    ofClear(0,0,0,255);
    fbo.end();
    
    bBrushDown = false;
}

//--------------------------------------------------------------
void ofApp::update(){
    
    // MASK (frame buffer object)
    //
    maskFbo.begin();
    if (bBrushDown){
        brushImg.draw(mouseX-25,mouseY-25,50,50);
    }
    maskFbo.end();
    
    // HERE the shader-masking happends
    //
    fbo.begin();
    // Cleaning everthing with alpha mask on 0 in order to make it transparent for default
    ofClear(0, 0, 0, 0); 
    
    shader.begin();
    shader.setUniformTexture("maskTex", maskFbo.getTexture(), 1 );
    
    srcImg.draw(0,0);

    shader.end();
    fbo.end();

}

//--------------------------------------------------------------
void ofApp::draw(){
    ofSetColor(255,255);
    
    dstImg.draw(0,0);
    
    fbo.draw(0,0);

    ofDrawBitmapString("Drag the Mouse to draw", 15,15);
    ofDrawBitmapString("Press spacebar to clear", 15, 30);
}

//--------------------------------------------------------------
void ofApp::keyPressed(int key){
    maskFbo.begin();
    ofClear(0,0,0,255);
    maskFbo.end();
}

//--------------------------------------------------------------
void ofApp::keyReleased(int key){

}

//--------------------------------------------------------------
void ofApp::mouseMoved(int x, int y ){

}

//--------------------------------------------------------------
void ofApp::mouseDragged(int x, int y, int button){

}

//--------------------------------------------------------------
void ofApp::mousePressed(int x, int y, int button){
    bBrushDown = true;
}

//--------------------------------------------------------------
void ofApp::mouseReleased(int x, int y, int button){
    bBrushDown = false;
}

//--------------------------------------------------------------
void ofApp::mouseEntered(int x, int y){

}

//--------------------------------------------------------------
void ofApp::mouseExited(int x, int y){

}

//--------------------------------------------------------------
void ofApp::windowResized(int w, int h){

}

//--------------------------------------------------------------
void ofApp::gotMessage(ofMessage msg){

}

//--------------------------------------------------------------
void ofApp::dragEvent(ofDragInfo dragInfo){ 

}