[Solved with Solution] Prevent picturebox from repainting

Question

Hello currently I'm programming some sort of displaying measurement results. So I drew nearly 30thousand dots on a pciturebox. A little bit slow but it works. Here's my problem: When painting is done and i drag a windows window over this painting the image starts to recreatet(reload) itself. Things I did so far: I painted everything on a bitmap file that is later on the picturebox with grafik.DrawImage(bitmap 0 0 bitmap.Width bitmap.Height); With this the image is drawn instantly and not dot for dot I also tried to set the image of the picturebox to the bitmap. But it results in a heavy laggy loop and doesn't solve my problem. I set a bool that says me the image is already drawn but if I drag a window over the image it gets just erased and due to my bool not repainted I want it like it is the picturebox's image then it would never reload... I hope you understood my problem. If not pls feel free to ask me. I attached my code. Thanks and best regarts.

Frogleg · Answer

You can create at form load Bitmap myBmp; private void Form1_Load(object sender EventArgs e) { pictureBox1.Image = createBmp(); } public Bitmap createBmp() { //draw your bitmap myBmp = new Bitmap(pictureBox1.Width pictureBox1.Height); Graphics g = Graphics.FromImage(myBmp); g.FillRectangle(Brushes.Blue00pictureBox1.Width pictureBox1.Height); return myBmp; } you don't need code in picturebox paint event Even if you load a jpg from your hdd it still needs to be loaded into memory to be accessed - the only advantage being form will load faster

Sascha B · Answer

Ok that doesn't work for me ... I made it like this: public void paintpicture(int tabnummer) { int w = 390 - 1 h = 390 - 1; Bitmap bitmap = new Bitmap(wh System.Drawing.Imaging.PixelFormat.Format32bppArgb); Graphics bmpgrafik = Graphics.FromImage(bitmap); bmpgrafik.CompositingMode = CompositingMode.SourceCopy; bmpgrafik.CompositingQuality = CompositingQuality.HighQuality; try{ bmpgrafik.FillRectangle(new SolidBrush(notenfarbe) x + w / 2 - dotstrength y * -1 + h / 2 - dotstrength dotstrength * 2 + 1 dotstrength * 2 + 1); }catch(Exception error) { ; } imagepreview[tabnummer].Image = bitmap; bitmap.Dispose(); bmpgrafik.Dispose(); } It only shows a red cross. I searched and google says that it could be a paint exception. But it never throws out an exception... If I made it in the paint event with grafik.DrawImage(bitmap 0 0 bitmap.Width bitmap.Height); Where grafik is Graphics grafik = e.Graphics instead of imagepreview[tabnummer].Image = bitmap; it works normal I really want it working. Have you an other idea? Thanks Edit: Something that work too is to save the bitmap first into a file and the load it with Image.FromFile(filename); But thats not really optimal... Solution : Sorry that I said your tipp didn't work. I was just that stupid and disposed the bitmap directly after setting it up :D So the code above works perfectly if you leave out bitmap.dispose();

Sascha B · Answer

ok that looks good. I'll try it today and give you a feedback tomorrow. Thanks for helping

Sascha B · Answer

That's what I already did... But if I use a picutrebox with a normale image path and not a virtual created bitmap then the image won't be redrawn every time O_o What's the differenz if I create the image in the paint event or just set the path? I thought they were both created in a paint event so both had to be redrawn. It would be very kind of you for teaching me. Thanks

Frogleg · Answer

When ever you minimize drag the picturebox\form or drag another window over the picturebox the image will have to be redrawn. Drawing to and then displaying a bitmap is the best way around your problem.