iOS 将图片转换成base64编码

- (BOOL) imageHasAlpha: (UIImage *) image

{

    CGImageAlphaInfo alpha =CGImageGetAlphaInfo(image.CGImage);

    return (alpha ==kCGImageAlphaFirst ||

            alpha == kCGImageAlphaLast ||

            alpha == kCGImageAlphaPremultipliedFirst ||

            alpha == kCGImageAlphaPremultipliedLast);

}

- (NSString *) image2DataURL: (UIImage *) image

{

    NSData *imageData =nil;

    NSString *mimeType =nil;

    

    if ([selfimageHasAlpha: image]) {

        imageData = UIImagePNGRepresentation(image);

        mimeType = @"image/png";

    } else {

        imageData = UIImageJPEGRepresentation(image,1.0f);

        mimeType = @"image/jpeg";

    }

    

    return [NSStringstringWithFormat:@"data:%@;base64,%@", mimeType,

            [imageData base64EncodedStringWithOptions:0]];

    

}