How to make a selectable image in a NSTextView?

Question

I am working on an application which performs some mathematical calculations and sends the results ( including texts and graphs) into a NSTextView.

This code works fine in making the output but this is the problem: I want that user can select/copy-pate and drag-drop the produced images into other text editors ( like Pages or Text Edit). When user drags an image from my textview, it is dragged but nothing is pasted to the destination:

- (void)drawRect:(NSRect)dirtyRect {
    [super drawRect:dirtyRect];

    NSBezierPath* aPath=[NSBezierPath bezierPath];

    NSImage* anImage = [[NSImage alloc] initWithSize:NSMakeSize(200.0, 200.0)];
    [anImage lockFocus];
    //some drawings:
    NSColor* blue= [NSColor blueColor];
    [blue setStroke];
    aPath=[NSBezierPath bezierPath];
    [aPath setLineWidth:20];
    [aPath moveToPoint:NSMakePoint(20.0, 20.0)];
    [aPath lineToPoint:NSMakePoint(100.0, 100.0)];
    [aPath stroke];
    [anImage unlockFocus];
    //re-capture and change it to a bitmap

    NSSize size = [anImage size];
    [anImage lockFocus];
    NSBitmapImageRep* rep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:NSMakeRect(0,0,size.width,size.height)];
    [anImage unlockFocus];
    NSData* jpgData = [rep representationUsingType:   NSJPEGFileType properties:nil ];

    NSImage* newImage= [[NSImage alloc]initWithData:jpgData];

    //append attrited string only once.   BOOL isDrownYet in header
    if (!isDrownYet) {
        NSTextAttachmentCell *attachmentCell1 = [[NSTextAttachmentCell alloc]   initImageCell:newImage];
        NSTextAttachment *attachment1 = [[NSTextAttachment alloc] init];
        [attachment1 setAttachmentCell: attachmentCell1];
        NSMutableAttributedString *attributedString1 = (NSMutableAttributedString*)[ NSMutableAttributedString attributedStringWithAttachment: attachment1];
        [self.textStorage appendAttributedString:attributedString1];
        isDrownYet=YES;
    }
 }