iOS开发- OpenGL ES屏幕截图

水深无声 2022-08-27 10:46 224阅读 0赞

之前写过一个常规的屏幕截图[:http://blog.csdn.net/hitwhylz/article/details/17189351][http_blog.csdn.net_hitwhylz_article_details_17189351]

但是发现这个办法对于OpenGL 无用。 获取到的数据为空。

所以这里介绍下OpenGL ES屏幕截图。

1.初始化。

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

2.声明方法。

- (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.使用

调用上述的方法即可。

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

[http_blog.csdn.net_hitwhylz_article_details_17189351]: http://blog.csdn.net/hitwhylz/article/details/17189351