iphone - 调整图像大小而不损失其质量

Question

当我将导入图像[其他图像]发送到服务器时，花费的时间比 iPhone 图像[通过默认相机拍照]要少。是否有选项可以在不损失质量的情况下调整图像大小？

Answer 1

使用此代码会有帮助

+ (UIImage *)scaleImage:(UIImage *)image maxWidth:(int) maxWidth maxHeight:(int) maxHeight
{
    CGImageRef imgRef = image.CGImage;
    CGFloat width = CGImageGetWidth(imgRef);
    CGFloat height = CGImageGetHeight(imgRef);

    if (width <= maxWidth && height <= maxHeight)
    {
        return image;
    }

    CGAffineTransform transform = CGAffineTransformIdentity;
    CGRect bounds = CGRectMake(0, 0, width, height);

    if (width > maxWidth || height > maxHeight)
    {
        CGFloat ratio = width/height;

        if (ratio > 1)
        {
            bounds.size.width = maxWidth;
            bounds.size.height = bounds.size.width / ratio;
        }
        else
        {
            bounds.size.height = maxHeight;
            bounds.size.width = bounds.size.height * ratio;
        }
    }

    CGFloat scaleRatio = bounds.size.width / width;
    UIGraphicsBeginImageContext(bounds.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(context, scaleRatio, -scaleRatio);
    CGContextTranslateCTM(context, 0, -height);
    CGContextConcatCTM(context, transform);
    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);

    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return imageCopy;

}