Question

我正在使用以下代码调整图像大小，使其适合我所拥有的uiimageview，但保持纵横比。问题是在某些图像上，例如用相机拍摄的肖像图像，它会因某种未知原因而垂直拉伸图像。任何解决方案？

我正在使用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

我不建议使用此方法，特别是如果您使用的是uiimageview

在imageview上设置图像，然后重置imageview的帧，图像将随之缩放

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

Answer 2

如何在代码中创建一些断点和NSLog，它会显示图像的大小。我记得如果你通过相机，它会改变图像的大小。最好的问候。

为什么这个UIImage调整代码不起作用？

2 个答案: