PDRPluginResult返回值最大长度

PDRPluginResult 返回值 的最大长度问题，插件压缩图片返回Base64字符串，但图片像素width大于450的时候，就返回不了值了。

if (command) {
NSString cid=[command.arguments objectAtIndex:0];
NSString url=[command.arguments objectAtIndex:1];
NSString pysb=[command.arguments objectAtIndex:2];
NSString lsWidth=[command.arguments objectAtIndex:3];
NSString *lsHeight=[command.arguments objectAtIndex:4];

    NSURL *aPath3=[NSURL URLWithString:url];  
    UIImage *img =[[UIImage alloc]initWithData:[NSData dataWithContentsOfURL:aPath3]];  
    float pysb2= [ pysb floatValue];  

    //新图片的长宽  
    int width=[lsWidth intValue];  
     float newwidth=width * pysb2;  
    if(newwidth>430){  
        newwidth=430;  
    }  
    NSData *imageData = nil;  
    NSString *mimeType = nil;  
    NSString *dataString=nil;  

    //压缩  
    UIImage *newImg=[self imageCompressForWidth:img targetWidth:newwidth];  

    if (UIImagePNGRepresentation(newImg) == nil) {  
        imageData = UIImageJPEGRepresentation(newImg, pysb2);  
        mimeType = @"image/jpeg";  
    } else {  
        imageData = UIImagePNGRepresentation(newImg);  
        mimeType = @"image/png";  
    }  
    dataString=[NSString stringWithFormat:@"%@",[imageData base64EncodedStringWithOptions: 0]];  
    PDRPluginResult *result = [PDRPluginResult resultWithStatus:PDRCommandStatusOK messageAsString:dataString];  
    [self toCallback:cid withReslut:[result toJSONString]];  
}  

//压缩方法
-(UIImage ) imageCompressForWidth:(UIImage )sourceImage targetWidth:(CGFloat)defineWidth{
UIImage newImage = nil;
CGSize imageSize = sourceImage.size;
CGFloat width = imageSize.width;
CGFloat height = imageSize.height;
CGFloat targetWidth = defineWidth;
CGFloat targetHeight = height / (width / targetWidth);
CGSize size = CGSizeMake(targetWidth, targetHeight);
CGFloat scaleFactor = 0.0;
CGFloat scaledWidth = targetWidth;
CGFloat scaledHeight = targetHeight;
CGPoint thumbnailPoint = CGPointMake(0.0, 0.0);
if(CGSizeEqualToSize(imageSize, size) == NO){
CGFloat widthFactor = targetWidth / width;
CGFloat heightFactor = targetHeight / height;
if(widthFactor > heightFactor){
scaleFactor = widthFactor;
}
else{
scaleFactor = heightFactor;
}
scaledWidth = width scaleFactor;
scaledHeight = height scaleFactor;
if(widthFactor > heightFactor){
thumbnailPoint.y = (targetHeight - scaledHeight) 0.5;
}else if(widthFactor < heightFactor){
thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
}
}
UIGraphicsBeginImageContext(size);
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumbnailPoint;
thumbnailRect.size.width = scaledWidth;
thumbnailRect.size.height = scaledHeight;

[sourceImage drawInRect:thumbnailRect];  

newImage = UIGraphicsGetImageFromCurrentImageContext();  
if(newImage == nil){  
    NSLog(@"scale image fail");  
}  

UIGraphicsEndImageContext();  
return newImage;  

}