在不损失图像质量的情况下调整图像大小的最佳方法是什么?

Question

实际上我已经使用了以下两种方法来调整图像大小，但是我的客户告诉我图像质量非常差，所以我想知道什么应该是图像调整大小的最佳方法。我只是截取屏幕截图，并将这张480x320大小的UIImage截图发送到以下功能。

- (UIImage *)makeResizedImage:(CGSize)newSize quality:(CGInterpolationQuality)interpolationQuality image:(UIImage *)inImage{
    NSLog(@"OriginalImage%f",inImage.size.width);
    CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
    CGImageRef imageRef = [inImage CGImage];
    // Compute the bytes per row of the new image
    size_t bytesPerRow = CGImageGetBitsPerPixel(imageRef) / CGImageGetBitsPerComponent(imageRef) * newRect.size.width;
    bytesPerRow = (bytesPerRow + 15) & ~15;  // Make it 16-byte aligned
    // Build a bitmap context that's the same dimensions as the new size
    CGContextRef bitmap = CGBitmapContextCreate(NULL,
                                                newRect.size.width,
                                                newRect.size.height,
                                                CGImageGetBitsPerComponent(imageRef),
                                                bytesPerRow,
                                                CGImageGetColorSpace(imageRef),
                                                CGImageGetBitmapInfo(imageRef));
    CGContextSetInterpolationQuality(bitmap, interpolationQuality);
    // Draw into the context; this scales the image
    CGContextDrawImage(bitmap, newRect, imageRef);
    // Get the resized image from the context and a UIImage
    CGImageRef resizedImageRef = CGBitmapContextCreateImage(bitmap);
    UIImage *resizedImage = [UIImage imageWithCGImage:resizedImageRef];
    NSLog(@"ResizedImage%f",resizedImage.size.width);
    NSLog(@"ResizedImage%f",resizedImage.size.height);
    // Clean up
    CGContextRelease(bitmap);
    CGImageRelease(resizedImageRef);
    return resizedImage;
}

或

- (UIImage *)resizedImage:(CGSize)newSize
                transform:(CGAffineTransform)transform
           drawTransposed:(BOOL)transpose
     interpolationQuality:(CGInterpolationQuality)quality {
    CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
    CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
    CGImageRef imageRef = self.CGImage;
    // Build a context that's the same dimensions as the new size
    CGContextRef bitmap = CGBitmapContextCreate(NULL,
                                                newRect.size.width,
                                                newRect.size.height,
                                                CGImageGetBitsPerComponent(imageRef),
                                                0,
                                                CGImageGetColorSpace(imageRef),
                                                CGImageGetBitmapInfo(imageRef));
    // Rotate and/or flip the image if required by its orientation
    CGContextConcatCTM(bitmap, transform);
    // Set the quality level to use when rescaling
    CGContextSetInterpolationQuality(bitmap, quality);
    // Draw into the context; this scales the image
    CGContextDrawImage(bitmap, transpose ? transposedRect : newRect, imageRef);
    // Get the resized image from the context and a UIImage
    CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
    // Clean up
    CGContextRelease(bitmap);
    CGImageRelease(newImageRef);
    return newImage;
}

请告诉我是否有其他方法可以在不影响图像质量的情况下调整图像大小

Answer 1

您可以尝试集成一个库，而不是使用自己的库。

这里有一个:http://code.google.com/p/simple-iphone-image-processing/