iOS开发中压缩图片的质量以及缩小图片尺寸

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://cloud.tencent.com/developer/article/1337688

-(UIImage *)resizeImage:(UIImage *)image

{

float actualHeight = image.size.height;

float actualWidth = image.size.width;

float maxHeight = 300.0;    // 图片的最大高度

float maxWidth = 400.0; // 图片的最大宽度

float imgRatio = actualWidth/actualHeight;

float maxRatio = maxWidth/maxHeight;

float compressionQuality = 0.5;//50 percent compression

if (actualHeight > maxHeight || actualWidth > maxWidth)

    {

if(imgRatio < maxRatio)

        {

//adjust width according to maxHeight

            imgRatio = maxHeight / actualHeight;

            actualWidth = imgRatio * actualWidth;

            actualHeight = maxHeight;

        }

else if(imgRatio > maxRatio)

        {

//adjust height according to maxWidth

            imgRatio = maxWidth / actualWidth;

            actualHeight = imgRatio * actualHeight;

            actualWidth = maxWidth;

        }

else

        {

            actualHeight = maxHeight;

            actualWidth = maxWidth;

        }

    }

CGRect rect = CGRectMake(0.0, 0.0, actualWidth, actualHeight);

UIGraphicsBeginImageContext(rect.size);

    image drawInRect:rect;

UIImage *img = UIGraphicsGetImageFromCurrentImageContext();

NSData *imageData = UIImageJPEGRepresentation(img, compressionQuality);

UIGraphicsEndImageContext();

return UIImage imageWithData:imageData;

}