CBitmapContextCreate、CGContextDrawImage、CGBitmapContextCreateImage 错误

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：无效上下文

错误：CGBitmapContextCreateImage：无效上下文

目前，我的应用程序在 OS 4.0 中完美运行，但我一直试图让它在 3.1.3 中正常工作，并且不断收到上述错误。

我对 iPhone 开发相当陌生，不太确定问题是什么。我正在使用在 stackoverflow 上的另一篇文章中找到的图像调整大小代码。

这是代码：

- (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; 

任何帮助将不胜感激。如果您需要更多信息，我很乐意发布。

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。行字节数至少需要是宽度乘以每个像素的字节数。