How to draw a bitmap element using OpenGL

In this topic

• Drawing a bitmap element using OpenGL
• Compiling a display list for the element's geometry
• Opening a bitmap and creating the OpenGL texture for that image
• Binding the texture to the OpenGL geometry and drawing it in the correct location
• Putting it all together

Drawing a bitmap element using OpenGL

• Visual C# programming language.
• ArcGIS Engine and ArcGIS Desktop architecture - This means that you know exactly when and where to plug in the OpenGL drawing (the custom layer drawing methods, Before/After draw event handlers, and so on). For more information, see RSS weather 3D layer.  
• Working knowledge of OpenGL - If you need to refresh your OpenGL knowledge, the following are some popular OpenGL Web sites:
  • NeHe Productions
  • OpenGL organization
  • OpenGL tutorial

Compiling a display list for the element's geometry

m_itemList=GL.glGenLists(1);

GL.glNewList(m_itemList, GL.GL_COMPILE);

GL.glPushMatrix();

GL.glTranslatef( - 0.5f,  - 0.5f, 0.0f);

GL.glTexEnvi(GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE, (int)GL.GL_MODULATE);
GL.glEnable(GL.GL_TEXTURE_2D);

GL.glBegin(GL.GL_QUADS);
GL.glTexCoord2f(0.0f, 0.0f);
GL.glVertex2f(0.0f, 0.0f);
GL.glTexCoord2f(0.0f, 1.0f);
GL.glVertex2f(0.0f, 1.0f);
GL.glTexCoord2f(1.0f, 1.0f);
GL.glVertex2f(1.0f, 1.0f);
GL.glTexCoord2f(1.0f, 0.0f);
GL.glVertex2f(1.0f, 0.0f);
GL.glEnd();

GL.glPopMatrix();

GL.glEndList();

Opening a bitmap and creating the OpenGL texture for that image

Bitmap bitmap=new Bitmap(@"FullImagePath");

private uint CreateTexture(Bitmap bitmap){}

int h=bitmap.Height;
int w=bitmap.Width;
int s=Math.Max(h, w);

double x=Math.Log(Convert.ToDouble(s)) / Math.Log(2.0);
s=Convert.ToInt32(Math.Pow(2.0, Convert.ToDouble(Math.Ceiling(x))));
int bufferSizeInPixels=s * s;

Rectangle rect=new Rectangle(0, 0, bitmap.Width, bitmap.Height);
bitmap.RotateFlip(RotateFlipType.RotateNoneFlipY);
System.Drawing.Imaging.BitmapData bitmapData;
bitmapData=bitmap.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadOnly,
    System.Drawing.Imaging.PixelFormat.Format24bppRgb);

byte[] bgrBuffer=new byte[bufferSizeInPixels * 3];

unsafe
{
    fixed(byte * pBgrBuffer=bgrBuffer)
    {
        GLU.gluScaleImage(GL.GL_BGR_EXT, bitmap.Size.Width, bitmap.Size.Height,
            GL.GL_UNSIGNED_BYTE, bitmapData.Scan0.ToPointer(), s, s,
            GL.GL_UNSIGNED_BYTE, pBgrBuffer);
    }
}

byte[] bgraBuffer=new byte[bufferSizeInPixels * 4];

int posBgr=0;
int posBgra=0;
for (int i=0; i < bufferSizeInPixels; i++)
{
    bgraBuffer[posBgra]=bgrBuffer[posBgr]; //This is the buffer value of B.
    bgraBuffer[posBgra + 1]=bgrBuffer[posBgr + 1]; //This is the buffer value of G.
    bgraBuffer[posBgra + 2]=bgrBuffer[posBgr + 2]; //This is the buffer value of R.

    //Sets the alpha buffer value.
    if (255 == bgrBuffer[posBgr] && 255 == bgrBuffer[posBgr + 1] && 255 ==
        bgrBuffer[posBgr + 2])
    {
        bgraBuffer[posBgra + 3]=0;
    }
    else
    {
        bgraBuffer[posBgra + 3]=255;
    }
    posBgr += 3;
    posBgra += 4;
}

uint[] texture=new uint[1];
GL.glEnable(GL.GL_TEXTURE_2D);
GL.glGenTextures(1, texture);
GL.glBindTexture(GL.GL_TEXTURE_2D, texture[0]);

GL.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MAG_FILTER, (int)GL.GL_LINEAR);
GL.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MIN_FILTER, (int)GL.GL_LINEAR);
GL.glTexEnvi(GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE, (int)GL.GL_MODULATE);

unsafe
{
    fixed(byte * pBgraBuffer=bgraBuffer)
    {
        GL.glTexImage2D(GL.GL_TEXTURE_2D, 0, (int)GL.GL_RGBA, s, s, 0,
            GL.GL_BGRA_EXT, GL.GL_UNSIGNED_BYTE, pBgraBuffer);
    }
}

bitmap.UnlockBits(bitmapData);

return texture[0];

Binding the texture to the OpenGL geometry and drawing it in the correct location

GL.glPushMatrix();

GL.glTranslatef((float)m_deviceFrame.left + 70.0f, (float)m_deviceFrame.top + 70.0f,
    0.0f);

GL.glScalef(scale, scale, 0.0f);

GL.glRotatef((float)rotation, 0.0f, 0.0f, 1.0f);

GL.glBindTexture(GL.GL_TEXTURE_2D, (uint)m_textureId);

GL.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);

GL.glCallList(m_itemList);

GL.glPopMatrix();

Putting it all together

void DrawMethod(� � �)
{
    if (m_bOnce)
    {
        CreateDisplayLists();
        Bitmap bitmap=new Bitmap(m_imagePath);
        m_textureId=CreateTexture(bitmap);

        m_bOnce=false;
    }

    //Draw the element.
    GL.glPushMatrix();
    GL.glTranslatef((float)m_deviceFrame.left + 70.0f, (float)m_deviceFrame.top +
        70.0f, 0.0f);
    GL.glScalef(scale, scale, 0.0f);
    GL.glRotatef((float)Display.DisplayTransformation.Rotation, 0.0f, 0.0f, 1.0f);
    GL.glBindTexture(GL.GL_TEXTURE_2D, (uint)m_textureId);
    GL.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
    GL.glCallList(m_itemList);
    GL.glPopMatrix();
}

See Also: