Ios 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？

事实上，我使用了以下两种方法来调整图像大小，但我的客户告诉我，图像质量非常差，所以我想知道调整图像大小的最佳方法是什么。 我只是截图并将这个480x320大小的UIImage截图发送到以下函数

- (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

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请告诉我是否有其他方法可以在不损失图像质量的情况下调整图像大小

您可以尝试集成一个库，而不是滚动自己的库

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这里有一个：

您可以尝试集成一个库，而不是滚动自己的库

---

这里有一个：

它们是如何失去质量的？像素化、模糊、拉伸或其他什么？它们是如何失去质量的？像素化、模糊、拉伸还是其他？

- (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;
}