调整从相机拉出的 UIimages 也会旋转 UIimage? [英] Resizing UIimages pulled from the Camera also ROTATES the UIimage?

问题描述

我正在从相机获取 UIimages 并将它们分配给 UIImageViews 以进行显示.当我这样做时，相机会给我一个 1200 x 1600 像素的图像，然后我将其分配给我的应用程序中的 UIImageView.在这种情况下，图像在图像视图中按预期显示.但是，当我在将检索到的 UIImage 分配给 UIImageView 之前尝试调整它的大小时，图像正在按预期调整大小，但在某处(在 RESIZING 代码中?)我的 UIImage 被旋转了......结果，当我将调整大小的 UIImage 分配给 UIImageView 时，图像被旋转 90 度并显示为拉伸，因为纵横比(1200 x 1600 像素)没有变化...

I am getting UIimages from the camera and assigning them to UIImageViews to be displayed. When I do this the camera gives me a 1200 x 1600 pixel image which I then assign to a UIImageView in my Application. The image is displayed as expected in the image view under this condition. However, when I attempt to RESIZE the retrieved UIImage before assigning it to the UIImageView, the image is resizing as expected but there IS a problem in that somewhere (in the RESIZING code?) my UIImage is getting ROTATED... As a result, when I assign the resized UIImage to a UIImageView the image is rotated 90 degrees and appears stretched as the aspect ratio (1200 x 1600 pixels) was unchanged...

我正在使用它从相机获取 UIImage:

- (void) imagePickerController:(UIImagePickerController*)picker didFinishPickingMediaWithInfo:(NSDictionary*)info
{

        myImg = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
        myResizedImg = [self resizeImage:myImg width:400 height:533];
        [myImageView setImage:myResizedImg];

}

我正在使用它来调整它的大小:

-(UIImage *)resizeImage:(UIImage *)anImage width:(int)width height:(int)height
{

    CGImageRef imageRef = [anImage CGImage];

    CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);

    if (alphaInfo == kCGImageAlphaNone)
    alphaInfo = kCGImageAlphaNoneSkipLast;


    CGContextRef bitmap = CGBitmapContextCreate(NULL, width, height, CGImageGetBitsPerComponent(imageRef), 4 * width, CGImageGetColorSpace(imageRef), alphaInfo);

    CGContextDrawImage(bitmap, CGRectMake(0, 0, width, height), imageRef);

    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage *result = [UIImage imageWithCGImage:ref];

    CGContextRelease(bitmap);
    CGImageRelease(ref);

    return result;  
}

问题:如何在不旋转像素的情况下调整从相机拉出的 UIImage 的大小?

推荐答案

您的代码不起作用的原因是您的代码上的 imageOrientation 没有被考虑在内.具体来说，如果 imageOrientation 是右/左，那么您需要旋转图像并交换宽度/高度.这里有一些代码可以做到这一点:

The reason your code doesn't work is because the imageOrientation on the code that you have is not being taken into account. Specifically, if the imageOrientation is right/left, then you need to both rotate the image and swap width/height. Here is some code to do this:

-(UIImage*)imageByScalingToSize:(CGSize)targetSize
{
    UIImage* sourceImage = self; 
    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;

    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);

    }   

    if (sourceImage.imageOrientation == UIImageOrientationLeft) {
        CGContextRotateCTM (bitmap, radians(90));
        CGContextTranslateCTM (bitmap, 0, -targetHeight);

    } else if (sourceImage.imageOrientation == UIImageOrientationRight) {
        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(0, 0, targetWidth, targetHeight), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage* newImage = [UIImage imageWithCGImage:ref];

    CGContextRelease(bitmap);
    CGImageRelease(ref);

    return newImage; 
}

这将调整您的图像大小并将其旋转到正确的方向.如果您需要弧度的定义，则为:

This will resize your image and rotate it to the correct orientation. If you need the definition for radians, it is:

static inline double radians (double degrees) {return degrees * M_PI/180;}

Daniel 给出的答案也是正确的，但它存在的问题是它不是线程安全的，因为您使用的是 UIGraphicsBeginImageContext().由于上面的代码只使用了CG功能，所以你已经准备好了.我也有一个类似的功能来调整图像的大小和进行适当的纵横填充 - 如果这就是你要找的，请告诉我.

The answer Daniel gave is also correct, but it suffers from the problem that it is not thread-safe, since you're using UIGraphicsBeginImageContext(). Since the above code only uses CG functions, you're all set. I also have a similar function to resize and do proper aspect fill on images - let me know if that's what you're looking for.

注意:我从这篇文章，并做了一些修改以使其适用于 JPEG.

Note: I got the original function from this post, and did some modifications to make it work on JPEGs.

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