How can I access the picture in my canvas?

OpenGL Development JOGL Development
#1

Last year this http://rogeralsing.com/2008/12/07/genetic-programming-evolution-of-mona-lisa/ got on Slashdot and I thought it was pretty neat. (Render some random polygons, compare the result with a picture of Mona Lisa, change the polygons around a bit, if the new picture is more similar to Mona Lisa than the old one use that as the base for future changes. Repeat).

I would like to make my own, so I installed Java and JOGL on my machine and have been tweeking the JOGL-example on wikipedia. http://en.wikipedia.org/wiki/Java_OpenGL

I have come as far as to render some random polygons, but now I would like to compare what it looks like with an image file.

How do I access the canvas and get it as a bitmap or similar so I can compare it at a pixel level to my picture of Mona Lisa? A fast way is better than a slow way, I expect to do this hundreds of thousands of times to get anywhere near the original picture.

#2

Use glReadPixels().

#3

u can use the snapshot class if you need the whole image

#4

glReadPixels is bogued on some graphics cards, especially some ATI FireGL.

Do you mean com.sun.opengl.util.awt.Screenshot?

#5

yup com.sun.opengl.util.awt.Screenshot

#6

That is so cool, just had to have a go!

Kev