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，所花费的时间比 iphone 图像 [通过默认相机拍照] 花费的时间少。是否可以选择调整图像大小而不损失其质量？

Answer 1

使用此代码将有所帮助

+ (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;

}

Answer 2

试试下面这个方法...

像下面这样打电话...

 UIImage *imgBig = [self imageWithImage:yourImage scaledToSize::yourNewImageSize];

并使用这种波纹管方法..

-(UIImage *)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{

    UIGraphicsBeginImageContextWithOptions(newSize, YES, image.scale);
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;

}