Question

I’m creating an application (Windows Form) that allows the user to take a screenshot based on the locations they choose (drag to select area). I wanted to add a little “preview pane” thats zoomed in so the user can select the area they want more precisely (larger pixels). On a mousemove event i have a the following code…

private void falseDesktop_MouseMove(object sender, MouseEventArgs e)
    {
        zoomBox.Image = showZoomBox(e.Location);
        zoomBox.Invalidate();
        bmpCrop.Dispose();
    }

private Image showZoomBox(Point curLocation)
    {
        Point start = new Point(curLocation.X - 50, curLocation.Y - 50);
        Size size = new Size(100, 90);
        Rectangle rect = new Rectangle(start, size);
        Image selection = cropImage(falseDesktop.Image, rect);
        return selection;
    }

private static Bitmap bmpCrop;
private static Image cropImage(Image img, Rectangle cropArea)
    {
        if (cropArea.Width != 0 && cropArea.Height != 0)
        {
            Bitmap bmpImage = new Bitmap(img);
            bmpCrop = bmpImage.Clone(cropArea, bmpImage.PixelFormat);
            bmpImage.Dispose();
            return (Image)(bmpCrop);
        }
        return null;
    }

The line that fails and has the Out of Memory exception is:

bmpCrop = bmpImage.Clone(cropArea, bmpImage.PixelFormat);

Basically what this does is it takes a 100×90 rectangle around the mouse pointer and pulls that into the zoomBox, which is a picturebox control. However, in the process, i get an Out Of Memory error. What is it that i am doing incorrectly here?

Thanks for your assistance.

Answer 1

Out of memory in C# imaging, is usually sign of wrong rect or point – a bit of red herring. I bet start has negative X or Y when error happens or the Size.Hight + Y or Size.Width + X is bigger than Hight or width of the image.