I want capture screen when any game is running with opengl

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Why is glReadPixels() failing in this code in iOS 6.0?

I am developing a game with OpenGL, need a screen shot when best shot taken and upload facebook but when i take screen shot its only black screen. what i do ? I also use code in link : take screen Programmatically of UIview+glview and similar code but no success.

i am suing code from : http://developer.apple.com/library/ios/#qa/qa1704/_index.html

But All code result an image in simulator not in device(in device only black or white)

The answer to the above-linked question (and my comment there) explains why your glReadPixels()-based code is returning a black image. You need to either capture the screen contents before they are presented or use retained backing. — Brad Larson, Jan 17 '13 at 17:29
i am using class which is subclass of OpenGLES2DView.In this class i want to take a screenshot, when use glReadPixels it's not worked in device but in simnulator go right. — Shiv Kumar Singh, Jan 23 '13 at 11:03
Again, read the answer there. The reason your capture is failing is that glReadPixels() cannot be used after your content has been rendered to the screen in iOS 6.0+. You need to either have retained backing turned on for your CAEAGLLayer, or use glReadPixels() before `-presentRenderbuffer:` is called. — Brad Larson, Jan 23 '13 at 15:20
yes, I forget that point but now my issue is solved. when device capture image go some slow means stop few miliseconds. — Shiv Kumar Singh, Jan 24 '13 at 09:19

score 0 · Answer 1 · answered Jan 17 '13 at 04:41

0

If you want to take screen shot then also try with that code & check:

    CGRect screenRect = [[UIScreen mainScreen] bounds];
    UIGraphicsBeginImageContextWithOptions(screenRect.size, NO, 0.0);
    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

answered Jan 17 '13 at 04:41

Vishal

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this code is generate a white image only not any graphics in my project. – Shiv Kumar Singh Jan 17 '13 at 06:16

score 0 · Answer 2 · answered Jan 17 '13 at 12:17

Try this this will take screenshot of view and save into device photo album.

-(IBAction)captureScreen:(id)sender
{
    UIGraphicsBeginImageContext(self.view.bounds.size);
    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *snapImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    UIImageWriteToSavedPhotosAlbum(snapImage, nil, nil, nil);
}

I want capture screen when any game is running with opengl

2 Answers2

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