Overlay Mouse Image in Cocoa / OSX

Question

I need to capture the framebuffer and save it into the file,
i am using son of grab example code to capture the buffer, but it doesn't give me the mouse pointer,

So i am drawming the mouse pointer by my own, please refer the below code snippet, everything works fine, except cursor is not drawn at proper place, there is a slightly deviation in x & y coordinate, form the Cocoa framework, i am getting mouse pointer location, it seems somehow i should get mouse cursor bounds, so the same rect i can use to draw the cursor,
Any idea, how to use Mousse location pointer to draw the mouse image at correct location?

-(CGImageRef)appendMouseCursor:(CGImageRef)pSourceImage{
    // get the cursor image 
    NSPoint mouseLoc; 
    mouseLoc = [NSEvent mouseLocation]; //get cur

    NSLog(@"Mouse location is x=%d,y=%d",(int)mouseLoc.x,(int)mouseLoc.y);

    // get the mouse image 
    NSImage *overlay    =   [[[NSCursor arrowCursor] image] copy];

    NSLog(@"Mouse location is x=%d,y=%d cursor width = %d, cursor height = %d",(int)mouseLoc.x,(int)mouseLoc.y,(int)[overlay size].width,(int)[overlay size].height);

    int x = (int)mouseLoc.x;
    int y = (int)mouseLoc.y;
    int w = (int)[overlay size].width;
    int h = (int)[overlay size].height;
    int org_x = x-w/2;
    int org_y = y-h/2;

    size_t height = CGImageGetHeight(pSourceImage);
    size_t width =  CGImageGetWidth(pSourceImage);
    int bytesPerRow = CGImageGetBytesPerRow(pSourceImage);

    unsigned int * imgData = (unsigned int*)malloc(height*bytesPerRow);

    // have the graphics context now, 
    CGRect bgBoundingBox = CGRectMake (0, 0, width,height);

    CGContextRef context =  CGBitmapContextCreate(imgData, width, 
                                                  height, 
                                                  8, // 8 bits per component 
                                                  bytesPerRow, 
                                                  CGImageGetColorSpace(pSourceImage), 
                                                  CGImageGetBitmapInfo(pSourceImage));

    // first draw the image 
    CGContextDrawImage(context,bgBoundingBox,pSourceImage);

    // then mouse cursor 
    CGContextDrawImage(context,CGRectMake(0, 0, width,height),pSourceImage);

    // then mouse cursor 
    CGContextDrawImage(context,CGRectMake(org_x, org_y, w,h),[overlay CGImageForProposedRect: NULL context: NULL hints: NULL] );


    // assuming both the image has been drawn then create an Image Ref for that 

    CGImageRef pFinalImage = CGBitmapContextCreateImage(context);

    CGContextRelease(context);

    return pFinalImage; /* to be released by the caller */
}  

Everything works fine, except, there is slightly deviation in the mouse position, from the

Answer 1

You need to take into account the mouse cursor's hot spot, which is the pixel in the cursor that is the "active point". You can get this from the -hotspot method of NSCursor which returns an NSPoint relative to the bottom-left corner of the cursor's coordinate system.

So your code should probably be something like:

NSPoint offset = [[NSCursor arrowCursor] hotSpot];

int org_x = (x - w/2) - offset.x;
int org_y = (y - h/2) - offset.y;