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POglReadPixels crashes on specific render buffer widths
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copied!<p>I need to read content of CAEAGLLayer, which has various widths and heights (based on background image size). on iPad emulator everything is okay, but on device I have crashes or weird horizontal lines instead of content. Crashes not happens on width, for example, from 537 to 544 pixels</p> <p>I'm using following code</p> <pre><code>- (UIImage*)image { // Get the size of the backing CAEAGLLayer glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer); glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth); glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight); NSInteger x = 0, y = 0, width = backingWidth, height = backingHeight; NSInteger dataLength = width * height * 4; GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte)); // Read pixel data from the framebuffer glPixelStorei(GL_PACK_ALIGNMENT, 4); glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data); // Create a CGImage with the pixel data // If your OpenGL ES content is opaque, use kCGImageAlphaNoneSkipLast to ignore the alpha channel // otherwise, use kCGImageAlphaPremultipliedLast CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL); CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB(); CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast, ref, NULL, true, kCGRenderingIntentDefault); // OpenGL ES measures data in PIXELS // Create a graphics context with the target size measured in POINTS NSInteger widthInPoints, heightInPoints; // if (NULL != UIGraphicsBeginImageContextWithOptions) { // // On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration // // Set the scale parameter to your OpenGL ES view's contentScaleFactor // // so that you get a high-resolution snapshot when its value is greater than 1.0 // CGFloat scale = eaglview.contentScaleFactor; // widthInPoints = width / scale; // heightInPoints = height / scale; // UIGraphicsBeginImageContextWithOptions(CGSizeMake( widthInPoints, heightInPoints), NO, scale); // } // else { // On iOS prior to 4, fall back to use UIGraphicsBeginImageContext widthInPoints = width; heightInPoints = height; UIGraphicsBeginImageContext(CGSizeMake(widthInPoints, heightInPoints)); // } CGContextRef cgcontext = UIGraphicsGetCurrentContext(); // UIKit coordinate system is upside down to GL/Quartz coordinate system // Flip the CGImage by rendering it to the flipped bitmap context // The size of the destination area is measured in POINTS CGContextSetBlendMode(cgcontext, kCGBlendModeCopy); CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, widthInPoints, heightInPoints), iref); // Retrieve the UIImage from the current context UIImage *image1 = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); // Clean up free(data); CFRelease(ref); CFRelease(colorspace); CGImageRelease(iref); return image1; } </code></pre>

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