iOS代码剪裁图片尺寸/压缩图片质量

最新推荐文章于 2025-05-23 15:06:20 发布

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最新推荐文章于 2025-05-23 15:06:20 发布

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本文链接：https://blog.youkuaiyun.com/TailOfFairyLu/article/details/84861821

本文介绍了一种使用Objective-C编程语言实现的图片尺寸调整和质量压缩的方法。通过UIGraphicsBeginImageContext和UIImageJPEGRepresentation函数，可以有效地改变图片大小并将其压缩至指定的文件大小以下，适用于移动应用和网页开发中对图片资源的优化。

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#pragma mark -----改变显示图片的尺寸—————
- (UIImage*) OriginImage:(UIImage*)image scaleToSize:(CGSize)size {
    UIGraphicsBeginImageContext(size); //size 为CGSize类型，即你所需要的图片尺寸
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return scaledImage; //返回的就是已经改变的图片
}


#pragma mark - 连续压缩图片到50K以下
    NSData *data = [self compressQualityImage:[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageArray[0]]]] andMaxLength:50000];//单位 byte

- (NSData *)compressQualityImage:(UIImage *)image andMaxLength:(NSInteger)maxLength {
    CGFloat compression = 1;
    NSData *data = UIImageJPEGRepresentation(image, compression);
    //NSLog(@"Before compressing quality, image size = %ld KB",data.length/1024);
    if (data.length < maxLength) return data;
    
    CGFloat max = 1;
    CGFloat min = 0;
    for (int i = 0; i < 6; ++i) {
        compression = (max + min) / 2;
        data = UIImageJPEGRepresentation(image, compression);
        //NSLog(@"Compression = %.1f", compression);
        //NSLog(@"In compressing quality loop, image size = %ld KB", data.length / 1024);
        if (data.length < maxLength * 0.9) {
            min = compression;
        } else if (data.length > maxLength) {
            max = compression;
        } else {
            break;
        }
    }
    //NSLog(@"After compressing quality, image size = %ld KB", data.length / 1024);
    if (data.length < maxLength) return data;
    UIImage *resultImage = [UIImage imageWithData:data];
    // Compress by size
    NSUInteger lastDataLength = 0;
    while (data.length > maxLength && data.length != lastDataLength) {
        lastDataLength = data.length;
        CGFloat ratio = (CGFloat)maxLength / data.length;
        //NSLog(@"Ratio = %.1f", ratio);
        CGSize size = CGSizeMake((NSUInteger)(resultImage.size.width * sqrtf(ratio)),
                                 (NSUInteger)(resultImage.size.height * sqrtf(ratio))); // Use NSUInteger to prevent white blank
        UIGraphicsBeginImageContext(size);
        [resultImage drawInRect:CGRectMake(0, 0, size.width, size.height)];
        resultImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        data = UIImageJPEGRepresentation(resultImage, compression);
        //NSLog(@"In compressing size loop, image size = %ld KB", data.length / 1024);
    }
    //NSLog(@"After compressing size loop, image size = %ld KB", data.length / 1024);
    return data;
}