Xcode屏幕截图EAGLContext [英] Xcode Screenshot EAGLContext

问题描述

可能重复:
如何从EAGLView获取UIImage?

Possible Duplicate:
How to get UIImage from EAGLView?

所以我只是想知道是否有人知道将EAGLContext中存储的内容保存为UIImage的任何方法.

So I was just wondering if anybody knows any way to save what is stored in an EAGLContext as a UIImage.

我当前正在使用:

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

在我拥有的其他应用程序中，它可以正常工作，但是很显然，EAGLContext没有.layer属性.我尝试过强制转换为UIView，但这-毫不奇怪-不起作用:

in other apps I have and this works fine, but obviously, EAGLContext doesn't have a .layer property. I've tried casting to UIView, but that - unsurprisingly - doesn't work:

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

我正在使用OpenGLES 1绘制UIView上的EAGLContext属性(从技术上讲是视图控制器上另一个UIView上的UIView上的EAGLContext，但我认为应该没有什么不同).

I am drawing to an EAGLContext property on a UIView (technically an EAGLContext on a UIView on another UIView on a View Controller, but I figure that shouldn't make any difference) using OpenGLES 1.

如果有人对此一无所知，即使只是我完全在吠叫一棵不可能的树，也请让我知道！

If anybody knows anything about this, even if its just that I'm completely barking up an impossible tree, please let me know!

马特

推荐答案

几天后，我终于有了一个可行的解决方案. Apple提供的代码可以从EAGLView生成UIImage.然后，由于UIKit上下颠倒，您只需要垂直翻转图像即可.我发现此方法的文档链接不再存在.

After a few days I finally got a working solution to this. There is code provided by Apple which produces an UIImage from an EAGLView. Then you simply need to flip the image vertically since UIKit is upside down. The link to the documentation where I found this method doesn't exist anymore.

捕获EAGLView的方法:

Method to capture EAGLView:

-(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;
}

这篇关于Xcode屏幕截图EAGLContext的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！