EAGLView到UIImage颜色转换问题 [英] EAGLView to UIImage color conversion issue
问题描述
我有一个EAGLView（取自Apple的例子）我可以使用以下代码成功转换为UIImage：
I have an EAGLView (taken from Apple's examples) which I can successfully convert to a UIImage using this code:
- (UIImage *)glToUIImage:(CGSize)size {
NSInteger backingWidth = size.width;
NSInteger backingHeight = size.height;
NSInteger myDataLength = backingWidth * backingHeight * 4;
// allocate array and read pixels into it.
GLuint *buffer = (GLuint *) malloc(myDataLength);
glReadPixels(0, 0, backingWidth, backingHeight, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
// gl renders "upside down" so swap top to bottom into new array.
for(int y = 0; y < backingHeight / 2; y++) {
for(int x = 0; x < backingWidth; x++) {
//Swap top and bottom bytes
GLuint top = buffer[y * backingWidth + x];
GLuint bottom = buffer[(backingHeight - 1 - y) * backingWidth + x];
buffer[(backingHeight - 1 - y) * backingWidth + x] = top;
buffer[y * backingWidth + x] = bottom;
}
}
// make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, myDataLength, releaseScreenshotData);
// prep the ingredients
const int bitsPerComponent = 8;
const int bitsPerPixel = 4 * bitsPerComponent;
const int bytesPerRow = 4 * backingWidth;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
// make the cgimage
CGImageRef imageRef = CGImageCreate(backingWidth, backingHeight, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, YES, renderingIntent);
CGColorSpaceRelease(colorSpaceRef);
CGDataProviderRelease(provider);
// then make the UIImage from that
UIImage *myImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return myImage;
}
void releaseScreenshotData(void *info, const void *data, size_t size) {
free((void *)data);
};
以下是我使用此方法转换为UIImage的代码：
And here is the code where I use this method to convert to a UIImage:
EAGLView *newView = [[EAGLView alloc] initWithImage:photo.originalImage];
[newView reshapeFramebuffer];
[newView drawView:theSlider.tag value:theSlider.value];
//the two lines above are how EAGLViews in Apple's examples are modified
photoItem *newPhoto = [[photoItem alloc] initWithImage:[self glToUIImage:photo.originalImage.size]];
我遇到的问题是，有时转换的UIImage与EAGLView的颜色不同。如果我对EAGLView应用高饱和度，或高亮度，低对比度和其他一些情况，则会发生这种情况。例如，如果我将高饱和度应用于EAGLView，然后转换为UIImage，图像的某些部分将比它想象的更亮。
The problem I am having is, sometimes the converted UIImage won't have the same colors as the EAGLView. This occurs if I apply a high saturation to the EAGLView, or high brigtness, or low contrast, and some other cases. For example, if I apply a high saturation to the EAGLView, and then convert to UIImage, some parts of the image will be brighter than what it's suppose to be.
所以我发现问题是伪装的EAGLView计时问题，类似于我之前的问题（ EAGLView to UIImage计时问题）。
So I discovered that the problem was a EAGLView timing issue in disguise, similar to my previous question here (EAGLView to UIImage timing question).
推荐答案
对于任何仍在乎的人，请看下面的评论：
For anyone that still cares see my comment below:
汤米，我终于入侵了解决方案。这是另一个EAGLView计时问题（实际上只在Saturation期间出现），我能够使用你的performSelector修复它：afterDelay：0.0方法。 Thx
Tommy, I finally hacked my way into a solution. It was another EAGLView timing issue (which only showed up during Saturation actually), and I was able to fix it with your performSelector:afterDelay:0.0 approach. Thx
此外，我建议任何编写iOS 5.0的人都要研究Core Image和GLKView。它们基本上可以调整图像属性（就像我在这里做的那样）和EAGLView到UIImage转换类型的东西要简单得多。
Also, I would recommend anyone coding for iOS 5.0 to look into Core Image and GLKView. They basically make your job of adjusting image properties (as I am doing here) and EAGLView to UIImage conversion type of stuff much simpler.
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