Question

I’m using the following code to resize an image so it fits inside a uiimageview i have, but keeping the aspect ratio. The problem is that on some images, such as portrait images taken with the camera, it stretches the image vertically for some unknown reason. Any solutions?

I’m using MGImageResizeScale.

- (UIImage *)imageToFitSize:(CGSize)fitSize method:(MGImageResizingMethod)resizeMethod
{
    float imageScaleFactor = 1.0;
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 40000
    if ([self respondsToSelector:@selector(scale)]) {
        imageScaleFactor = [self scale];
    }
#endif

    float sourceWidth = [self size].width * imageScaleFactor;
    float sourceHeight = [self size].height * imageScaleFactor;
    float targetWidth = fitSize.width;
    float targetHeight = fitSize.height;
    BOOL cropping = !(resizeMethod == MGImageResizeScale);

    // Calculate aspect ratios
    float sourceRatio = sourceWidth / sourceHeight;
    float targetRatio = targetWidth / targetHeight;

    // Determine what side of the source image to use for proportional scaling
    BOOL scaleWidth = (sourceRatio <= targetRatio);
    // Deal with the case of just scaling proportionally to fit, without cropping
    scaleWidth = (cropping) ? scaleWidth : !scaleWidth;

    // Proportionally scale source image
    float scalingFactor, scaledWidth, scaledHeight;
    if (scaleWidth) {
        scalingFactor = 1.0 / sourceRatio;
        scaledWidth = targetWidth;
        scaledHeight = round(targetWidth * scalingFactor);
    } else {
        scalingFactor = sourceRatio;
        scaledWidth = round(targetHeight * scalingFactor);
        scaledHeight = targetHeight;
    }
    float scaleFactor = scaledHeight / sourceHeight;

    // Calculate compositing rectangles
    CGRect sourceRect, destRect;
    if (cropping) {
        destRect = CGRectMake(0, 0, targetWidth, targetHeight);
        float destX, destY;
        if (resizeMethod == MGImageResizeCrop) {
            // Crop center
            destX = round((scaledWidth - targetWidth) / 2.0);
            destY = round((scaledHeight - targetHeight) / 2.0);
        } else if (resizeMethod == MGImageResizeCropStart) {
            // Crop top or left (prefer top)
            if (scaleWidth) {
                // Crop top
                destX = 0.0;
                destY = 0.0;
            } else {
                // Crop left
                destX = 0.0;
                destY = round((scaledHeight - targetHeight) / 2.0);
            }
        } else if (resizeMethod == MGImageResizeCropEnd) {
            // Crop bottom or right
            if (scaleWidth) {
                // Crop bottom
                destX = round((scaledWidth - targetWidth) / 2.0);
                destY = round(scaledHeight - targetHeight);
            } else {
                // Crop right
                destX = round(scaledWidth - targetWidth);
                destY = round((scaledHeight - targetHeight) / 2.0);
            }
        }
        sourceRect = CGRectMake(destX / scaleFactor, destY / scaleFactor, 
                                targetWidth / scaleFactor, targetHeight / scaleFactor);
    } else {
        sourceRect = CGRectMake(0, 0, sourceWidth, sourceHeight);
        destRect = CGRectMake(0, 0, scaledWidth, scaledHeight);
    }

    // Create appropriately modified image.
    UIImage *image = nil;
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 40000
    if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 4.0) {
        UIGraphicsBeginImageContextWithOptions(destRect.size, NO, 0.0); // 0.0 for scale means "correct scale for device's main screen".
        CGImageRef sourceImg = CGImageCreateWithImageInRect([self CGImage], sourceRect); // cropping happens here.
        image = [UIImage imageWithCGImage:sourceImg scale:0.0 orientation:self.imageOrientation]; // create cropped UIImage.
        [image drawInRect:destRect]; // the actual scaling happens here, and orientation is taken care of automatically.
        CGImageRelease(sourceImg);
        image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
#endif
    if (!image) {
        // Try older method.
        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
        CGContextRef context = CGBitmapContextCreate(NULL, fitSize.width, fitSize.height, 8, (fitSize.width * 4), 
                                                     colorSpace, kCGImageAlphaPremultipliedLast);
        CGImageRef sourceImg = CGImageCreateWithImageInRect([self CGImage], sourceRect);
        CGContextDrawImage(context, destRect, sourceImg);
        CGImageRelease(sourceImg);
        CGImageRef finalImage = CGBitmapContextCreateImage(context);    
        CGContextRelease(context);
        CGColorSpaceRelease(colorSpace);
        image = [UIImage imageWithCGImage:finalImage];
        CGImageRelease(finalImage);
    }

    return image;
}

Answer 1

I do not suggest this method especially if you are using a uiimageview

set the image on the imageview then reset the frame of the imageview and the image will scale with it

imageView.image = someImage;
imageView.frame = CGRectMake(imageView.frame.origin.x, imageView.frame.origin.y, 30,30);