iOS 图片修改尺寸

/// 修改单张图片大小
/// - Parameters:
///   - image: 原始图片
///   - width: 目标宽度
- (UIImage *)fixImageSizeWithImage:(UIImage *)image width:(CGFloat)width
{
    CGSize size = image.size;
    if (size.width == width) {
        return image;
    }
    //计算目标图片高度
    CGFloat height = width * (size.height/size.width);
    //目标大小
    CGSize newSize = CGSizeMake(width, height);
    UIGraphicsBeginImageContextWithOptions(newSize, NO, [UIScreen mainScreen].scale);
    [image drawInRect:CGRectMake(0, 0, width, height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

/// 多张图片拼接成长图
/// - Parameters:
///   - images: 需要拼接的图片
///   - width: 目标图片的宽度
- (UIImage *)stitchImageWithImages:(NSArray<UIImage *> *)images width:(CGFloat)width
{
    CGFloat height = 0;
    NSMutableArray *newImages = [NSMutableArray array];
    for (UIImage *image in images) {
        UIImage *newImage = [self fixImageSizeWithImage:image width:width];
        [newImages addObject:newImage];
        height += newImage.size.height;
    }
    CGSize size = CGSizeMake(width, height);
    UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);
    CGFloat Y = 0;
    for (int i = 0; i < newImages.count; i++) {
        UIImage *image = newImages[i];
        if (i > 0) {
            UIImage *proImage = newImages[i - 1];
            Y = Y + proImage.size.height;
        }
        [image drawInRect:CGRectMake(0,Y, width, image.size.height)];
    }
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}