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POScreenshot of OpenGL ES content for Paint app
 

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  1. POScreenshot of OpenGL ES content for Paint app
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    <p>I’m working on a paint app for iphone. In my code I'm using an imageView which contain outline image on which I am puting CAEAGLLayer for filling colors in outline image. Now I am taking screenshot of OpenGL ES [CAEAGLLayer] rendered content using function:</p> <pre><code>- (UIImage*)snapshot:(UIView*)eaglview{ GLint backingWidth1, backingHeight1; // Bind the color renderbuffer used to render the OpenGL ES view // If your application only creates a single color renderbuffer which is already bound at this point, // this call is redundant, but it is needed if you're dealing with multiple renderbuffers. // Note, replace "_colorRenderbuffer" with the actual name of the renderbuffer object defined in your class. glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer); // Get the size of the backing CAEAGLLayer glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &amp;backingWidth1); glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &amp;backingHeight1); NSInteger x = 0, y = 0, width = backingWidth1, height = backingHeight1; 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 *image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); // Clean up free(data); CFRelease(ref); CFRelease(colorspace); CGImageRelease(iref); return image;} </code></pre> <p>combining this screenshot with outline image using function:</p> <pre><code>- (void)Combine:(UIImage *)Back{ UIImage *Front =backgroundImageView.image; //UIGraphicsBeginImageContext(Back.size); UIGraphicsBeginImageContext(CGSizeMake(640,960)); // Draw image1 [Back drawInRect:CGRectMake(0, 0, Back.size.width*2, Back.size.height*2)]; // Draw image2 [Front drawInRect:CGRectMake(0, 0, Front.size.width*2, Front.size.height*2)]; UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext(); UIImageWriteToSavedPhotosAlbum(resultingImage, nil, nil, nil); UIGraphicsEndImageContext(); </code></pre> <p>}</p> <p>Save this image to photoalbum using function </p> <pre><code> -(void)captureToPhotoAlbum { [self Combine:[self snapshot:self]]; UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Success" message:@"Image saved to Photo Album" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release]; } </code></pre> <p>Above Code is working but the image quality of screenshot is poor. On the outlines of the brush, there is a grayish outline. I have uploaded a screenshot of my app which is combination of opengles content &amp; UIImage.</p> <p><img src="https://i.stack.imgur.com/1Zkkd.jpg" alt="Screenshot"></p> <p>Is there any way to get retina display screenshot of opengles-CAEaglelayer content.</p> <p>Thank you in advance!</p>
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