gdi+

I understand it is best practise to call Dispose() on instances of Pen and Brush , except if they've been set to the system-predefined values (eg. System.Drawing.Brushes , System.Drawing.Pens or System.Drawing.SystemBrushes ) Trying to dispose a system-defined resource results in an exception being thrown. It doesn't appear to be obvious how you can detect (apart from wrapping the Dispose() call in a try/catch) whether one of these resources is referencing a system-defined or user-defined value. There is no requirement to call Dispose . The purpose of garbage collection is to eliminate these

I'm using .NET to make an application with a drawing surface, similar to Visio. The UI connects two objects on the screen with Graphics.DrawLine. This simple implementation works fine, but as the surface gets more complex, I need a more robust way to represent the objects. One of these robust requirements is determining the intersection point for two lines so I can indicate separation via some kind of graphic. So my question is, can anyone suggest a way to do this? Perhaps with a different technique (maybe GraphViz) or an algorithm? The representation of lines by y = mx + c is problematic for

Am i allowed to use a DC outside of a paint cycle? Is my window's DC guaranteed to be valid forever? i'm trying to figure out how long my control's Device Context (DC) is valid. i know that i can call: GetDC(hWnd); to get the device context of my control's window, but is that allowed? When Windows sends me a WM_PAINT message, i am supposed to call BeginPaint / EndPaint to properly acknowledge that i've painted it, and to internally clear the invalid region: BeginPaint(hWnd, {out}paintStruct); try //Do my painting finally EndPaint(hWnd, paintStruct); end; But calling BeginPaint also returns me

This is a bit puzzling here. The following code is part of a little testing application to verify that code changes didn't introduce a regression. To make it fast we used memcmp which appears to be the fastest way of comparing two images of equal size (unsurprisingly). However, we have a few test images that exhibit a rather surprising problem: memcmp on the bitmap data tells us that they are not equal, however, a pixel-by-pixel comparison doesn't find any difference at all. I was under the impression that when using LockBits on a Bitmap you get the actual raw bytes of the image. For a 24 bpp

In Photoshop you can select "Color" (the second from the bottom) to set the blending mode to the next lower layer: If you have just a gradient on top of an image the result could look like this: The description of the color blending mode I found somewhere is: Color changes the hue and saturation of the lower layer to the hue and saturation of the upper layer but leaves luminosity alone. My code so far is: using(var g = Graphics.FromImage(canvas)) { // draw the lower image g.DrawImage(lowerImg, left, top); // creating a gradient and draw on top using (Brush brush = new LinearGradientBrush(new

I use the code below to render a transparent icon: private void button1_Click(object sender, EventArgs e) { // using LoadCursorFromFile from user32.dll var cursor = NativeMethods.LoadCustomCursor(@"d:\Temp\Cursors\Cursors\aero_busy.ani"); // cursor -> bitmap Bitmap bitmap = new Bitmap(48, 48, PixelFormat.Format32bppArgb); Graphics gBitmap = Graphics.FromImage(bitmap); cursor.DrawStretched(gBitmap, new Rectangle(0, 0, 32, 32)); // 1. Draw bitmap on a form canvas Graphics gForm = Graphics.FromHwnd(this.Handle); gForm.DrawImage(bitmap, 50, 50); // 2. Draw cursor directly to a form canvas cursor

I'm drawing a custom diagram of business objects using .NET GDI+. Among other things, the diagram consists of several lines that are connecting the objects. In a particular scenario, I need to shorten a line by a specific number of pixels, let's say 10 pixels, i.e. find the point on the line that lies 10 pixels before the end point of the line. Imagine a circle with radius r = 10 pixels, and a line with start point (x1, y1) and end point (x2, y2). The circle is centered at the end point of the line, as in the following illustration. How do I calculate the point marked with a red circle, i.e.