屏幕截图代码可以在Simulator中完美运行，但不能在iOS Device中运行

Question

这是我的屏幕快照代码，可保存在库中或发送电子邮件。 问题是，它在Simulator中运行良好，但是当我在Device中运行此代码时，无论在屏幕上什么，它只会显示白色图像。 我已经尝试过同时使用iOS 5和iOS 6，但没有运气我应该错了的原因是什么

    NSInteger myDataLength = 320 * 430 * 4;
    GLubyte *buffer1 = (GLubyte *) malloc(myDataLength);
    GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);    

    //Read image memory form OpenGL
    glReadPixels(0, 50, 320, 430, GL_RGBA, GL_UNSIGNED_BYTE, buffer1);

    //Invert result image buffer into secondary buffer
    for(int y = 0; y < 430; y++)    {
        for(int x = 0; x < 320 * 4; x++) {
            buffer2[(429 - y) * 320 * 4 + x] = buffer1[y * 4 * 320 + x];
        }
    }

    //Create bitmap context
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef destContext = CGBitmapContextCreate(buffer2, 320, 430, 8, 320 * 4, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

    //Get image from context
    CGImageRef resultContext = CGBitmapContextCreateImage(destContext);
    UIImage *resultImg = [UIImage imageWithCGImage: resultContext];
    CGImageRelease(resultContext);

    //Send to mail or Save to PhotoLibrary
    if (sendMail) {
        [self emailImage: resultImg];
    } else {
        UIImageWriteToSavedPhotosAlbum(resultImg, nil, nil, nil);
    }

    //Release allocated memory
//  [resultImg release];
    free(buffer2);
    free(buffer1);
    CGContextRelease(destContext);
    CGColorSpaceRelease(colorSpace);

有没有我正在使用的任何类，模拟器都支持该类，而不是该设备？如果是，那么哪个类，因为据我搜索，我什么都没找到。

Answer 1

我发现我上面的代码很完美，问题不在这里。实际上问题出在

eaglLayer.drawableProperties

我已经从此代码更改

eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:

            [NSNumber numberWithBool:NO],  
                kEAGLDrawablePropertyRetainedBacking, 
                kEAGLColorFormatRGB565, 
                kEAGLDrawablePropertyColorFormat, nil];

对此

eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:

                [NSNumber numberWithBool:YES],  
                    kEAGLDrawablePropertyRetainedBacking, 
                    kEAGLColorFormatRGB565, 
                    kEAGLDrawablePropertyColorFormat, nil];

我刚设定

        kEAGLDrawablePropertyRetainedBacking = YES

谢谢上帝，一切正常。 但不知道为什么有人知道请告诉我

Answer 2

试试这个，它在设备上对我来说很完美：

+ (UIImage *)imageFromView:(UIView *)view inRect:(CGRect)rect {
    CGFloat screenScale = [[UIScreen mainScreen] scale];
    if ([view respondsToSelector:@selector(contentSize)]) {
        UIScrollView *scrollView = (UIScrollView *)view;
        UIGraphicsBeginImageContextWithOptions(scrollView.contentSize, NO, screenScale);
    } else {
        UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, screenScale);
    }
    CGContextRef resizedContext = UIGraphicsGetCurrentContext();
    [view.layer renderInContext:resizedContext];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    image = [UIImage imageWithCGImage:CGImageCreateWithImageInRect(image.CGImage, CGRectMake(rect.origin.x*screenScale, rect.origin.y*screenScale, rect.size.width*screenScale, rect.size.height*screenScale))];
    UIGraphicsEndImageContext();
    return [image imageScaledToSize:CGSizeMake(rect.size.width, rect.size.height)];
}

- (UIImage *)imageScaledToSize:(CGSize)newSize {
    if ((self.size.width == newSize.width) && (self.size.height == newSize.height)) {
        return self;
    }
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [self drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newImage;
}