Xcode Screenshot EAGLContext [重复]

Question

可能重复：
How to get UIImage from EAGLView?

所以我只是想知道是否有人知道任何方法可以将存储在 EAGLContext 中的内容保存为 UIImage。

我目前正在使用：

UIGraphicsBeginImageContext(CGSizeMake(768, 1024));
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

在我拥有的其他应用程序中，这工作正常，但显然，EAGLContext 没有 .layer 属性。我已经尝试投射到 UIView，但是这 - 不出所料 - 不起作用：

UIView *newView = [[UIView alloc] init];
newView = (UIView *)context;

我正在使用 OpenGLES 1 绘制到 UIView 上的 EAGLContext 属性（技术上是视图控制器上另一个 UIView 上的 UIView 上的 EAGLContext，但我认为这不应该有任何区别）。

如果有人知道这件事，即使只是我完全在吠叫一棵不可能的树，请告诉我！

马特

Answer 1

几天后，我终于找到了一个可行的解决方案。 Apple 提供了从 EAGLView 生成 UIImage 的代码。然后你只需要垂直翻转图像，因为 UIKit 是倒置的。我发现此方法的文档链接已不存在。

捕捉EAGLView的方法：

-(UIImage *)drawableToCGImage 
{
    GLint backingWidth2, backingHeight2;
    //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, &backingWidth2);
    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight2);

    NSInteger x = 0, y = 0, width2 = backingWidth2, height2 = backingHeight2;
    NSInteger dataLength = width2 * height2 * 4;
    GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte));

    // Read pixel data from the framebuffer
    glPixelStorei(GL_PACK_ALIGNMENT, 4);
    glReadPixels(x, y, width2, height2, 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(width2, height2, 8, 32, width2 * 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 = self.contentScaleFactor;
        widthInPoints = width2 / scale;
        heightInPoints = height2 / scale;
        UIGraphicsBeginImageContextWithOptions(CGSizeMake(widthInPoints, heightInPoints), NO, scale);
    }
    else {
        // On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
        widthInPoints = width2;
        heightInPoints = height2;
        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;
}

垂直翻转图像的方法：

- (UIImage *)flipImageVertically:(UIImage *)originalImage 
{
    UIImageView *tempImageView = [[UIImageView alloc] initWithImage:originalImage];
    UIGraphicsBeginImageContext(tempImageView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGAffineTransform flipVertical = CGAffineTransformMake(
                                                           1, 0, 0, -1, 0, tempImageView.frame.size.height
                                                           );
    CGContextConcatCTM(context, flipVertical);

    [tempImageView.layer renderInContext:context];

    UIImage *flippedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    //[tempImageView release];

    return flippedImage;
}