IOS development-OpenGL ES screenshots

 

However, this method is useless for OpenGL. The retrieved data is empty.

So here we will introduce the OpenGL ES screen.

 

1. initialization.

 

 

CAEAGLLayer *eaglLayer = (CAEAGLLayer *) self.layer;  eaglLayer.drawableProperties = @{      kEAGLDrawablePropertyRetainedBacking: [NSNumber numberWithBool:YES],      kEAGLDrawablePropertyColorFormat: kEAGLColorFormatRGBA8  }; 

 

2. Declare the method.

 

- (UIImage*)snapshot:(UIView*)eaglview{    GLint backingWidth, backingHeight;        // 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 viewRenderbuffer 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, &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 *image = UIGraphicsGetImageFromCurrentImageContext();                UIGraphicsEndImageContext();        // Clean up        free(data);        CFRelease(ref);        CFRelease(colorspace);        CGImageRelease(iref);        return image;}

 

 

 

3. Use

Call the preceding method.

-(UIImage *) snapshot :( UIView *) eaglview