Convert ofFbo to ofxCvColorImage for blur effect

beginners
#1

I’d like to process my drawing pitcture with blur effect.
For the reason, drawing figures in ofFbo and convert ofFbo memory to ofxCvColorImage.
But, drawing ofxCvColorImage cause curious figures.

#include "ofApp.h"

ofFbo buffer;
ofxTrueTypeFontUC font;
ofPixels pixels;
ofImage image;
ofxCvColorImage colorImage;
//--------------------------------------------------------------
void ofApp::setup(){
    ofSetWindowShape(1280, 720);
    ofSetFrameRate(30);
    ofBackground(0, 0, 0);
    font.loadFont("Meiryo.ttf", 48);
    buffer.allocate(800, 800, GL_RGBA);
    colorImage.allocate(800, 800);
    buffer.begin();
    {
        ofBackground(0, 0, 0);
        ofSetColor(255, 255, 255, 255);
        ofCircle(50,50, 50);
        font.drawString("hoge", 200, 200);
    }
    buffer.end();
    buffer.readToPixels(pixels);
    image.setFromPixels(pixels);
}
//--------------------------------------------------------------
void ofApp::update(){}
//--------------------------------------------------------------
void ofApp::draw(){
    colorImage.setFromPixels(image.getPixelsRef());
    colorImage.blurGaussian(5);
    colorImage.draw(0, 0);
}
#2

Seems that colorImage is allocated as RGB and it should be RGBA (OF_IMAGE_COLOR_ALPHA). Else, you could allocate the ofFbo as GL_RGB.

#3

How do I allocate image as RGBA?

ofxCvImage::allocate(int w, int h)

I think allocate method only accept these two arguments(width, height).

#4

Can’t see how either… It might be best to allocate your ofFbo as GL_RGB then.

buffer.allocate(800,800, GL_RGB);

Notice that ofxCvColorImage has a hardcoded iplchannels set to 3. So it’s not possible to use an alpha (fourth) channel on it.

I haven’t use these myself, but it is kind of weird that there isn’t a ofxCvColorAlphaImage or similar…Maybe you can use the ofxCvFloatImage for that.

PS: Consider ofxCv, it’s less constrained as it only wraps OpenCV… might be a bit harder to use though.

#5

I want to try effect for only text simply on an image.
In other words, draw and compose two figures; effected text and non-effected any images.
What methods are effective or easily to implement?