UIImagePickerController的编辑功能会将UIImage锁定到最大尺寸为320x320。

Question

更新：

随着iPhone OS 3.0+的推出，整个UIImagePickerController API已经发生了变化。本问答应被视为2.2版本的旧代码。

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当使用UIImagePickerController并允许编辑图像时，iPhone会允许用户调整和平移图像。但是，编辑后的图像最大尺寸被限制在320x320。

例如，我拍了一张iPhone截图并将其放置在照片库中，这是一个480x320的png文件。当我使用UIImagePickerController选择该图像时，即使我不缩放或平移图像，它也会在从UIImagePickerController返回之前被裁剪为320x320。但是，如果我关闭编辑功能，则会以正确的480x320大小返回图像。

我的理论： 非常微妙地，iPhone显示了两个非标准的半透明工具栏，覆盖在图像上方。这些工具栏在照片上留下一个无害的320x320的“窗口”。看起来，这个窗口有效地裁剪了底层的照片。

注意： 回调还返回一个编辑字典，其中包含原始图像和裁剪矩形，但矩形当然也是最大320x320。

有没有想法如何允许缩放和平移大于320x320的图像？

一些代码：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)img editingInfo:(NSDictionary *)editInfo {

        self.myImageView.userInteractionEnabled=YES;
        CGRect imageFrame = myImageView.frame;
        CGPoint imageCenter = myImageView.center;
        imageFrame.size = img.size;
        myImageView.frame = imageFrame;
        self.myImageView.image = img;
        myImageView.center = imageCenter;

        [self dismissModalViewControllerAnimated:YES];
        [self performSelector:@selector(hideToolBars) withObject:nil afterDelay:2.0];
    }

- Corey Floyd

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我在3.0.1上仍然看到这个问题，这在3.1中修复了吗？ - Jasarien

Answer 1

正如Craig所说，这是开发论坛和苹果常规讨论版面上的一个问题。然而，我找到了一个解决方法。我正在使用来自以下网址的代码片段：Apple Dev Forums。

其中包含了大部分你需要的内容，并且解决了所有相机方向问题。我添加了以下内容，它将接受编辑信息并使用它来获取原始裁剪矩形，并加以修改：

- (UIImage*)scaleImage:(UIImage*)anImage withEditingInfo:(NSDictionary*)editInfo{

    UIImage *newImage;

    UIImage *originalImage = [editInfo valueForKey:@"UIImagePickerControllerOriginalImage"];
    CGSize originalSize = CGSizeMake(originalImage.size.width, originalImage.size.height);
    CGRect originalFrame;
    originalFrame.origin = CGPointMake(0,0);
    originalFrame.size = originalSize;

    CGRect croppingRect = [[editInfo valueForKey:@"UIImagePickerControllerCropRect"] CGRectValue];
    CGSize croppingRectSize = CGSizeMake(croppingRect.size.width, croppingRect.size.height);

    CGSize croppedScaledImageSize = anImage.size;

    float scaledBarClipHeight = 80;

    CGSize scaledImageSize;
    float scale;

    if(!CGSizeEqualToSize(croppedScaledImageSize, originalSize)){

        scale = croppedScaledImageSize.width/croppingRectSize.width;
        float barClipHeight = scaledBarClipHeight/scale;

        croppingRect.origin.y -= barClipHeight;
        croppingRect.size.height += (2*barClipHeight);

        if(croppingRect.origin.y<=0){
            croppingRect.size.height += croppingRect.origin.y;
            croppingRect.origin.y=0;
        }

        if(croppingRect.size.height > (originalSize.height - croppingRect.origin.y)){
            croppingRect.size.height = (originalSize.height - croppingRect.origin.y);
        }


        scaledImageSize = croppingRect.size;
        scaledImageSize.width *= scale;
        scaledImageSize.height *= scale;

        newImage =  [self cropImage:originalImage to:croppingRect andScaleTo:scaledImageSize];

    }else{

        newImage = originalImage;

    }

    return newImage;
}

我将回调方法从开发者论坛帖子中更新为以下内容：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)img editingInfo:(NSDictionary *)editInfo {

    [self dismissModalViewControllerAnimated:YES];
    self.myImageView.userInteractionEnabled=YES;
    CGRect imageFrame = myImageView.frame;
    CGPoint imageCenter = myImageView.center;
    UIImage *croppedImage;


    NSMutableDictionary *imageDescriptor = [editInfo mutableCopy];

    // CGFloat scaleSize = 400.0f;
    CGFloat scaleSize = 640.0f;
    switch ([picker sourceType]) {
            //done
        case UIImagePickerControllerSourceTypePhotoLibrary:
            croppedImage = [self scaleImage:img withEditingInfo:editInfo];
            [imageDescriptor setObject:croppedImage forKey:@"croppedImage"];
            break;


        case UIImagePickerControllerSourceTypeCamera: {
            UIImageOrientation originalOrientation = [[editInfo objectForKey:UIImagePickerControllerOriginalImage] imageOrientation];
            if (originalOrientation != UIImageOrientationUp) {
                NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
                CGRect origRect;
                [[editInfo objectForKey:UIImagePickerControllerCropRect] getValue:&origRect];
                UIImage *rotatedImage = straightenAndScaleImage([editInfo objectForKey:UIImagePickerControllerOriginalImage], scaleSize);
                CGFloat scale = scaleSize/1600.0f;
                origRect.origin.x *= scale;
                origRect.origin.y *= scale;
                origRect.size.width *= scale;
                origRect.size.height *= scale;
                croppedImage = [self cropImage:rotatedImage to:origRect andScaleTo:CGSizeMake(320, 480)];
                [imageDescriptor setObject:croppedImage forKey:@"croppedImage"];
                [pool drain];
            }
            else {
                croppedImage = [self scaleImage:img withEditingInfo:editInfo];
                [imageDescriptor setObject:croppedImage forKey:@"croppedImage"];
            }
        }
            break;

        case UIImagePickerControllerSourceTypeSavedPhotosAlbum: {
            UIImageOrientation originalOrientation = [[editInfo objectForKey:UIImagePickerControllerOriginalImage] imageOrientation];
            if (originalOrientation != UIImageOrientationUp) {
                NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
                CGRect origRect;
                [[editInfo objectForKey:UIImagePickerControllerCropRect] getValue:&origRect];
                UIImage *rotatedImage = straightenAndScaleImage([editInfo objectForKey:UIImagePickerControllerOriginalImage], scaleSize);
                CGFloat scale = scaleSize/640.0f;
                origRect.origin.x *= scale;
                origRect.origin.y *= scale;
                origRect.size.width *= scale;
                origRect.size.height *= scale;
                croppedImage = [self cropImage:rotatedImage to:origRect andScaleTo:CGSizeMake(320, 480)];
                [imageDescriptor setObject:croppedImage forKey:@"croppedImage"];
                [pool drain];
            }
            else {
                croppedImage = [self scaleImage:img withEditingInfo:editInfo];
                [imageDescriptor setObject:croppedImage forKey:@"croppedImage"];
            }
        }
            break;
        default:
            break;
    }

    imageFrame.size = croppedImage.size;
    myImageView.frame = imageFrame;
    myImageView.image = [imageDescriptor objectForKey:@"croppedImage"];
    myImageView.center = imageCenter;


}

- Corey Floyd

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不要这样写： CGSize originalSize = CGSizeMake(originalImage.size.width, originalImage.size.height);可以这样简写： CGSize originalSize = originalImage.size.width; - Frank Szczerba

@Frank - 我想你的意思是你可以直接使用CGSize originalSize = originalImage.size; - Brian

@Brian - 是的，那就是我想说的。不确定.width是怎么进去的。你应该因为发现了一个三年前的错误而获得某种徽章！ - Frank Szczerba

Answer 2

我可能来晚了回答这个问题，但是我有更好的方法来完成这项工作。

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

+(UIImage*)editedImageFromMediaWithInfo:(NSDictionary*)info{
    if(![info   objectForKey:UIImagePickerControllerCropRect])return nil;
    if(![info   objectForKey:UIImagePickerControllerOriginalImage])return nil;

    UIImage *originalImage=[info objectForKey:UIImagePickerControllerOriginalImage];
    CGRect rect=[[info objectForKey:UIImagePickerControllerCropRect] CGRectValue];

    CGImageRef imageRef = CGImageCreateWithImageInRect([originalImage CGImage], rect);

    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
    CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);
    CGContextRef bitmap = CGBitmapContextCreate(NULL, rect.size.width, rect.size.height, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

    if (originalImage.imageOrientation == UIImageOrientationLeft) {
        CGContextRotateCTM (bitmap, radians(90));
        CGContextTranslateCTM (bitmap, 0, -rect.size.height);

    } else if (originalImage.imageOrientation == UIImageOrientationRight) {
        CGContextRotateCTM (bitmap, radians(-90));
        CGContextTranslateCTM (bitmap, -rect.size.width, 0);

    } else if (originalImage.imageOrientation == UIImageOrientationUp) {
        // NOTHING
    } else if (originalImage.imageOrientation == UIImageOrientationDown) {
        CGContextTranslateCTM (bitmap, rect.size.width, rect.size.height);
        CGContextRotateCTM (bitmap, radians(-180.));
    }

    CGContextDrawImage(bitmap, CGRectMake(0, 0, rect.size.width, rect.size.height), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);

    UIImage *resultImage=[UIImage imageWithCGImage:ref];
    CGImageRelease(imageRef);
    CGContextRelease(bitmap);
    CGImageRelease(ref);

    return resultImage;
}

这个方法只是使用相对的CropRect来裁剪原始图像，虽然不会对图像进行缩放，但对于我来说它简洁明了。仅供参考 :)

- b123400

Answer 3

随着iPhone OS 3.0+的推出，整个UIImagePickerController API已经发生了变化。这个问题和答案应该被视为2.2版本的遗留代码。

尽管你进行了警告，但我还是花费了宝贵的开发时间才意识到iOS 3.0+给我们提供了UIImagePickerControllerEditedImage，这使得处理手动裁剪用户的缩放和处理方向变得不必要。

如果有人仍在使用UIImagePickerControllerOriginalImage，并试图弄清楚如何通过UIImagePickerControllerCropRect等方式最好地应用裁剪，则不再需要此操作。

- pandelic

Answer 4

迟到总比不来得好：这里是orientationTransformForImage函数的源代码

CGAffineTransform orientationTransformForImage(UIImage *image, CGSize *newSize) {
    CGImageRef img = [image CGImage];
    CGFloat width = CGImageGetWidth(img);
    CGFloat height = CGImageGetHeight(img);
    CGSize size = CGSizeMake(width, height); 
    CGAffineTransform transform = CGAffineTransformIdentity; 
    CGFloat origHeight = size.height;
    UIImageOrientation orient = image.imageOrientation; 
    switch(orient) { /* EXIF 1 to 8 */
        case UIImageOrientationUp:
            break;
        case UIImageOrientationUpMirrored:
            transform = CGAffineTransformMakeTranslation(width, 0.0f);
            transform = CGAffineTransformScale(transform, -1.0f, 1.0f);
            break;
        case UIImageOrientationDown:
            transform = CGAffineTransformMakeTranslation(width, height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformMakeTranslation(0.0f, height);
            transform = CGAffineTransformScale(transform, 1.0f, -1.0f);
            break;
        case UIImageOrientationLeftMirrored:
            size.height = size.width;
            size.width = origHeight;
            transform = CGAffineTransformMakeTranslation(height, width);
            transform = CGAffineTransformScale(transform, -1.0f, 1.0f);
            transform = CGAffineTransformRotate(transform, 3.0f * M_PI / 2.0f);
            break;
        case UIImageOrientationLeft:
            size.height = size.width;
            size.width = origHeight;
            transform = CGAffineTransformMakeTranslation(0.0f, width);
            transform = CGAffineTransformRotate(transform, 3.0f * M_PI / 2.0f);
            break;
        case UIImageOrientationRightMirrored:
            size.height = size.width;
            size.width = origHeight;
            transform = CGAffineTransformMakeScale(-1.0f, 1.0f);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0f);
            break;
        case UIImageOrientationRight:
            size.height = size.width;
            size.width = origHeight;
            transform = CGAffineTransformMakeTranslation(height, 0.0f);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0f);
            break;
        default:
            ;
    }
    *newSize = size; 
    return transform; 
}

- Bill Garrison

Answer 5

这似乎是SDK的一个阻碍，至少在将allowsImageEditing设置为图像选择器中的TRUE时是如此。在苹果论坛上有关于这个主题的一些讨论：

http://discussions.apple.com/message.jspa?messageID=7841993

- Craig Otis

Answer 6

我写了一个关于UIImage的类别, 它提供了全分辨率裁剪。最简单的安装方式是使用CocoaPods, 将UIImage-ImagePickerCrop添加到你的podfile中。

#import <UIImage+ImagePickerCrop.h>

...

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo: (NSDictionary *)info {
    [self dismissViewControllerAnimated:YES completion:nil];

    UIImage *croppedImage = [UIImage croppedImageWithImagePickerInfo:info];
    ...
}

- Frank Schmitt