关键就是压到微信需要的大小
直接贴代码

- (UIImage *)handleImageWithURLStr:(NSString *)imageURLStr {
    
    NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:[kHTTP_HEAD stringByAppendingString:imageURLStr]]];
    NSData *newImageData = imageData;
    // 压缩图片data大小
    newImageData = UIImageJPEGRepresentation([UIImage imageWithData:newImageData scale:0.1], 0.1f);
    UIImage *image = [UIImage imageWithData:newImageData];
    
    // 压缩图片分辨率(因为data压缩到一定程度后，如果图片分辨率不缩小的话还是不行)
    CGSize newSize = CGSizeMake(200, 200);
    UIGraphicsBeginImageContext(newSize);
    [image drawInRect:CGRectMake(0,0,(NSInteger)newSize.width, (NSInteger)newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

2017.7.5更新——压缩图片至指定大小

首先压缩图片有两种方法，一种压缩图片文件大小，一种压缩图片尺寸，百度都能知道，就不多说了。

1、压缩文件大小方法如下，此方法不能循环使用，因为压缩到一定比例再调用该方法就无效了

// 压缩图片
- (UIImage *)scaleImageCompression:(UIImage *)image {
    CGFloat origanSize = [self getImageLengthWithImage:image];
    
    NSData *imageData = UIImageJPEGRepresentation(image, 1);
    if (origanSize > 1024) {
        imageData=UIImageJPEGRepresentation(image, 0.1);
    } else if (origanSize > 512) {
        imageData=UIImageJPEGRepresentation(image, 0.5);
    }
    UIImage *image1 = [UIImage imageWithData:imageData];
    return image1;
}

2、这里是压缩到指定尺寸的关键代码，maxSize是想要压缩到的尺寸，单位kb。
建议先使用方法一压缩之后，再采取方法二压缩

// 压缩图片尺寸
- (UIImage *)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
    // Create a graphics image context
    NSInteger newWidth = (NSInteger)newSize.width;
    NSInteger newHeight = (NSInteger)newSize.height;
    UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight));
    
    // Tell the old image to draw in this new context, with the desired
    // new size
    
    [image drawInRect:CGRectMake(0 , 0,newWidth, newHeight)];
    
    // Get the new image from the context
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    // End the context
    UIGraphicsEndImageContext();
    
    // Return the new image.
    return newImage;
}

- (CGFloat)getImageLengthWithImage:(UIImage *)image {
    NSData * imageData = UIImageJPEGRepresentation(image,1);
    CGFloat length = [imageData length]/1000;
    return length;
}