Question

我从相机获取UIimages并将它们分配给UIImageViews进行显示。当我这样做时，相机给我一个1200 x 1600像素的图像，然后我分配给我的应用程序中的UIImageView。在此条件下，图像在图像视图中按预期显示。但是，当我在将其分配给UIImageView之前尝试调整检索到的UIImage时，图像正在按预期调整大小但是在某处（在RESIZING代码中？）我的UIImage正在进行ROTATED ...结果，当我将调整大小的UIImage分配给UIImageView时，图像旋转90度并在宽高比（1200 x 1600像素）不变的情况下显示为拉伸...

我正在使用它从相机中获取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？

Answer 1

您的代码无效的原因是因为您没有考虑代码中的imageOrientation。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。以下是一些代码：

-(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; 
}

这将调整图像大小并将其旋转到正确的方向。如果你需要弧度的定义，它是：

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

Daniel给出的答案也是正确的，但它遇到的问题是它不是线程安全的，因为你正在使用UIGraphicsBeginImageContext（）。由于上面的代码只使用CG函数，所以你都已经设置好了。我也有类似的功能来调整大小并对图像进行适当的填充 - 请告诉我这是否是您正在寻找的。

注意：我从this post获得了原始函数，并进行了一些修改以使其适用于JPEG。

Answer 2

我有一些代码也有这个问题，我发现这个代码有效，检查出来，让我知道你发现了什么

+ (UIImage*)imageWithImage:(UIImage*)image 
               scaledToSize:(CGSize)newSize;
{
   UIGraphicsBeginImageContext( newSize );
   [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
   UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   return newImage;
}

Answer 3

Swift 3

我将此添加到didFinishPickingMediaWithInfo方法，然后使用image而不必担心其轮换。

var image = info[UIImagePickerControllerOriginalImage] as! UIImage
if (image.imageOrientation != .up) {
  UIGraphicsBeginImageContextWithOptions(image.size, false, image.scale)
  image.draw(in: CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))
  image = UIGraphicsGetImageFromCurrentImageContext()!
  UIGraphicsEndImageContext()
}

Answer 4

如果要通过在两侧按宽度或高度裁剪矩形图像（无论是水平还是垂直）制作方形图像，请使用我的代码。不同之处在于我不伸展，但是我裁剪。我是通过修改顶部代码制作的：

//Cropping _image to fit it to the square by height or width

CGFloat a = _image.size.height;
CGFloat b = _image.size.width;
CGRect cropRect;

if (!(a==b)) {
    if (a<b) {
        cropRect = CGRectMake((b-a)/2.0, 0, a, a);
        b = a;
    }
    else if (b<a) {
        cropRect = CGRectMake(0, (a-b)/2.0, b, b);
        a = b;
    }

    CGImageRef imageRef = CGImageCreateWithImageInRect([_image CGImage], cropRect);

    UIImage* sourceImage = _image; 
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
    CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);
    CGContextRef bitmap;
    if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
        bitmap = CGBitmapContextCreate(NULL, a, a, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

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

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

    } else if (sourceImage.imageOrientation == UIImageOrientationRight) {
        CGContextRotateCTM (bitmap, radians(-90));
        CGContextTranslateCTM (bitmap, -a, 0);

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

    CGContextDrawImage(bitmap, CGRectMake(0, 0, a, a), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    _image = [UIImage imageWithCGImage:ref];
    CGImageRelease(imageRef);
}

调整从相机中提取的UIimages的大小也会旋转UIimage？

4 个答案: