ios图片裁剪压缩(2019最新算法)

也许打代码就是喜欢看到知识与成长的一部分吧

image.png

+ (UIImage *)sourceImage:(UIImage *)sourceImage targetSize:(CGSize)targetSize{
    CGFloat souceImageW = sourceImage.size.width;
    CGFloat souceImageH = sourceImage.size.height;
    if (souceImageH == 0 || souceImageW == 0) {
        return sourceImage;
    }
    BOOL isBiggerH = souceImageH > souceImageW;
    CGFloat targetW = isBiggerH ? MIN(targetSize.width, targetSize.height) : MAX(targetSize.width, targetSize.height);
    CGFloat targetH = isBiggerH ? MAX(targetSize.width, targetSize.height) : MIN(targetSize.width, targetSize.height);
    CGFloat coefficientW = targetW * 1.0 / souceImageW;
    CGFloat coefficientH = targetH * 1.0 / souceImageH ;
    CGFloat finalCoefficient = MIN(coefficientW, coefficientH);
    if (finalCoefficient > 1) {
        return sourceImage;   // 不需要缩小
    }else{
        CGPoint thumbnailPoint =CGPointMake(0.0,0.0);//这个是图片剪切的起点位置
        UIGraphicsBeginImageContext(CGSizeMake(MIN(finalCoefficient * souceImageW, targetW), MIN(finalCoefficient * souceImageH, targetH)));//开始剪切
        CGRect thumbnailRect =CGRectZero;//剪切起点(0,0)
        thumbnailRect.origin= thumbnailPoint;
        thumbnailRect.size.width= souceImageW * finalCoefficient;
        thumbnailRect.size.height= souceImageH * finalCoefficient;
        [sourceImage drawInRect:thumbnailRect];
        UIImage*newImage =UIGraphicsGetImageFromCurrentImageContext();//截图拿到图片
        return newImage;
    }
}