CBitmapContextCreate、CGContextDrawImage、CGBitmapContextCreateImage出错

Question

错误: CGBitmapContextCreate:无效数据字节/行:对于8个整数位/组件，3个组件，kCGImageAlphaNoneSkipFirst，应至少为400。

错误: CGContextDrawImage:无效的上下文

错误: CGBitmapContextCreateImage:无效的上下文

目前，我的应用程序在OS4.0上运行的很好，但我一直在尝试让它在3.1.3中正常工作，我一直收到上面提到的错误。

我是iPhone开发的新手，不太确定问题会是什么。我正在使用我在stackoverflow上的另一篇文章中找到的图像调整代码。

代码如下：

- (UIImage*)imageWithImage:(UIImage*)sourceImage scaledToSizeWithSameAspectRatio:(CGSize)targetSize{  
CGSize imageSize = sourceImage.size;
CGFloat width = imageSize.width;
CGFloat height = imageSize.height;
CGFloat targetWidth = targetSize.width;
CGFloat targetHeight = targetSize.height;
CGFloat scaleFactor = 0.0;
CGFloat scaledWidth = targetWidth;
CGFloat scaledHeight = targetHeight;
CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
    CGFloat widthFactor = targetWidth / width;
    CGFloat heightFactor = targetHeight / height;

    if (widthFactor > heightFactor) {
        scaleFactor = widthFactor; // scale to fit height
    }
    else {
        scaleFactor = heightFactor; // scale to fit width
    }

    scaledWidth  = width * scaleFactor;
    scaledHeight = height * scaleFactor;

    // center the image
    if (widthFactor > heightFactor) {
        thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
    }
    else if (widthFactor < heightFactor) {
        thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
    }
}     

CGImageRef imageRef = [sourceImage CGImage];
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);

if (bitmapInfo == kCGImageAlphaNone) {
    bitmapInfo = kCGImageAlphaNoneSkipLast;
}

CGContextRef bitmap;

if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
    bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

} else {
    bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

}       

// In the right or left cases, we need to switch scaledWidth and scaledHeight,
// and also the thumbnail point
if (sourceImage.imageOrientation == UIImageOrientationLeft) {
    thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x);
    CGFloat oldScaledWidth = scaledWidth;
    scaledWidth = scaledHeight;
    scaledHeight = oldScaledWidth;

    CGContextRotateCTM (bitmap, radians(90));
    CGContextTranslateCTM (bitmap, 0, -targetHeight);

} else if (sourceImage.imageOrientation == UIImageOrientationRight) {
    thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x);
    CGFloat oldScaledWidth = scaledWidth;
    scaledWidth = scaledHeight;
    scaledHeight = oldScaledWidth;

    CGContextRotateCTM (bitmap, radians(-90));
    CGContextTranslateCTM (bitmap, -targetWidth, 0);

} else if (sourceImage.imageOrientation == UIImageOrientationUp) {
    // NOTHING
} else if (sourceImage.imageOrientation == UIImageOrientationDown) {
    CGContextTranslateCTM (bitmap, targetWidth, targetHeight);
    CGContextRotateCTM (bitmap, radians(-180.));
}

CGContextDrawImage(bitmap, CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledWidth, scaledHeight), imageRef);
CGImageRef ref = CGBitmapContextCreateImage(bitmap);
UIImage* newImage = [UIImage imageWithCGImage:ref];

CGContextRelease(bitmap);
CGImageRelease(ref);

return newImage; 

任何帮助都将不胜感激。如果你需要更多的信息，我很乐意把它张贴出来。

Answer 1

第一个错误告诉您，将CGImageGetBitsPerComponent(imageRef)作为新位图上下文的行字节传递是不正确的。行字节数需要至少是宽度乘以每像素的字节数。