UIImage
。今天要和大家分享的是UIImage
的缩放。两种缩放:
size
.- (UIImage*)imageCompressWithSimple:(UIImage*)image scaledToSize:(CGSize)size{ UIGraphicsBeginImageContext(size); [image drawInRect:CGRectMake(0,0,size.width,size.height)]; UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return newImage;}
- (UIImage*)imageCompressWithSimple:(UIImage*)image scale:(float)scale{ CGSize size = image.size; CGFloat width = size.width; CGFloat height = size.height; CGFloat scaledWidth = width * scale; CGFloat scaledHeight = height * scale; UIGraphicsBeginImageContext(size); // this will crop [image drawInRect:CGRectMake(0,0,scaledWidth,scaledHeight)]; UIImage* newImage= UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return newImage;}
scale
是缩放系数 。
- (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize{ UIImage *sourceImage = [UIImage imageNamed:@"test.jpg"]; UIImage *newImage = nil; CGSize imageSize = sourceImage.size; CGFloat width = imageSize.width; CGFloat height = imageSize.height; CGFloat targetWidth = targetSize.width; CGFloat targetHeight = targetSize.height; CGFloat scaleFactor = 0.0; CGFloat scaledWidth = targetWidth; CGFloat scaledHeight = targetHeight; CGPoint thumbnailPoint = CGPointMake(0.0,0.0); if (CGSizeEqualToSize(imageSize, targetSize) == NO) { CGFloat widthFactor = targetWidth / width; CGFloat heightFactor = targetHeight / height; if (widthFactor > heightFactor) scaleFactor = widthFactor; // scale to fit height else scaleFactor = heightFactor; // scale to fit width scaledWidth= width * scaleFactor; scaledHeight = height * scaleFactor; // center the image if (widthFactor > heightFactor) { thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; } else if (widthFactor < heightFactor) { thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5; } } UIGraphicsBeginImageContext(targetSize); // this will crop CGRect thumbnailRect = CGRectZero; thumbnailRect.origin = thumbnailPoint; thumbnailRect.size.width= scaledWidth; thumbnailRect.size.height = scaledHeight; [sourceImage drawInRect:thumbnailRect]; newImage = UIGraphicsGetImageFromCurrentImageContext(); if(newImage == nil) NSLog(@"could not scale image"); //pop the context to get back to the default UIGraphicsEndImageContext(); return newImage;}
很久之前写了一篇文章解决MWPhotoBrowser中的SDWebImage加载大图导致的内存警告问题。这个我记得当时从服务器拿到的照片大概有10几M的样子,加载出来会导致内存警告。所以我当时通过修改SDWebImage源码,就是把下载下来的照片进行缩放,内存就降下来了。一般情况下应该不会加载这么大的照片的,用户要是知道,早把你的APP给删掉了。
作者李刚是刚刚在线( www.superqq.com )站长,百度百家专栏作者
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