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Texture mapping a .png into a rectangle and paint geometries

Posted Wednesday, 11 July, 2012 - 19:45 by Frank Lioty in

Hi guy,
I'm really new with OpenGL and I have some problems with texture mapping. I need to paint a .png (with transparency) and some lines and squares. I tried with TexLib but it render (correctly) just the texture with no geometries. So I'm trying to myself. This is my code:

    private void Form1_Load(object sender, EventArgs e) {
      bitmap = new Bitmap(@"c:\tiles\bitmask\pap.png");
      GL.Enable(EnableCap.Texture2D);
      GL.Hint(HintTarget.PerspectiveCorrectionHint, HintMode.Nicest);
      //naming e binding
      GL.GenTextures(1, out texture);
      GL.BindTexture(TextureTarget.Texture2D, texture);
      BitmapData data = bitmap.LockBits(new System.Drawing.Rectangle(0, 0, bitmap.Width, bitmap.Height),
                ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
      GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, data.Width, data.Height, 0,
          OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, data.Scan0);
      bitmap.UnlockBits(data);
 
      GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Linear);
      GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear);
      GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, data.Width, data.Height, 0,
                OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, data.Scan0);
 
    }

here the paint one:

    private void editor_Paint(object sender, PaintEventArgs e) {
      if (!loaded) return;
      GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
 
      GL.MatrixMode(MatrixMode.Modelview);
      GL.LoadIdentity();
 
      //hotspots
      for (int i = 0; i < arrays.Length; i++ ) {
        for (int j = 0; j < arrays[i].Count; j++) {
          //bitmask
          GL.BindTexture(TextureTarget.Texture2D, texture);
          GL.Begin(BeginMode.Quads);
          GL.TexCoord2(0, 0); GL.Vertex2(arrays[i][j].X, arrays[i][j].Y);
          GL.TexCoord2(1, 0); GL.Vertex2(arrays[i][j].X + arrays[i][j].Width, arrays[i][j].Y);
          GL.TexCoord2(1, 1); GL.Vertex2(arrays[i][j].X + arrays[i][j].Width, arrays[i][j].Y + arrays[i][j].Height);
          GL.TexCoord2(0, 1); GL.Vertex2(arrays[i][j].X, arrays[i][j].Y + arrays[i][j].Height);
          GL.End();
          //handler
          GL.Color3(colors[i]);
          GL.Begin(BeginMode.Quads);
          GL.Vertex2(arrays[i][j].Center.X - 4, arrays[i][j].Center.Y - 4);
          GL.Vertex2(arrays[i][j].Center.X + 4, arrays[i][j].Center.Y - 4);
          GL.Vertex2(arrays[i][j].Center.X + 4, arrays[i][j].Center.Y + 4);
          GL.Vertex2(arrays[i][j].Center.X - 4, arrays[i][j].Center.Y + 4);
          GL.End();
        }
      }

but it paints a black box (the .png) and all the geometries are not in their color but also in black. Any suggest?

‹ Wierd texture over polygon transparency problem VBO instancing example ›

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mOfl's picture

Re: Texture mapping a .png into a rectangle and paint ...

Posted Thursday, 12 July, 2012 - 14:20 by mOfl

The geometry is drawn, but in solid black color? Maybe try calling GL.Enable(EnableCap.Texture2D) somewhere at the beginning.

Frank Lioty's picture

Re: Texture mapping a .png into a rectangle and paint ...

Posted Thursday, 12 July, 2012 - 20:41 by Frank Lioty

it's there, the second instruction. Damn I'm going crazy!

Frank Lioty's picture

Re: Texture mapping a .png into a rectangle and paint ...

Posted Thursday, 12 July, 2012 - 22:01 by Frank Lioty

if I try to only paint my .png it works (with no transparency). But if I try to draw a red line, my .png become red, his content is visible but red-tinted:

In order:

- my .png
- a red filled square
- a white not-filled square