调整从相机中提取的UIimages的大小也会旋转UIimage？

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...

我正在使用它来从相机获取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？

Answer 1

您的代码不起作用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 - 让我知道这是否是你正在寻找的.

注意:我从这篇文章中获得了原始函数,并进行了一些修改以使其适用于JPEG.

Answer 2

我也遇到了一些代码,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;
}