Draw image with OpenGL

Question

How to draw video/image over map (GMap.Net) with open OpenGL/OpenTK (video from drone)

My question is how to draw video image on map since video can be looked with different angle on map and image should be trapezoid on the map and not quad?

I copied image from other question... Currently my code bellow draw quad but in quad I see 2 triangles which are not equal.

Current code:

public override void OnRender()
{
    if (!backgroundColor.HasValue)
        backgroundColor = new Pen(Fill).Color;
    GL.Color4(backgroundColor.Value);

    lock (bitmapSync)
    {
        if (bitmap != null)
            createTexture();
    }

    GL.Enable(EnableCap.Texture2D);
    GL.BindTexture(TextureTarget.Texture2D, texture);

    GL.Begin(PrimitiveType.Quads);
    {
        //TODO this works fine only for correct square image and not for trapezoid 
        GL.TexCoord2(0, 0); GL.Vertex2(LocalPoints[0].X, LocalPoints[0].Y);
        GL.TexCoord2(1, 0); GL.Vertex2(LocalPoints[1].X, LocalPoints[1].Y);
        GL.TexCoord2(1, 1); GL.Vertex2(LocalPoints[2].X, LocalPoints[2].Y);
        GL.TexCoord2(0, 1); GL.Vertex2(LocalPoints[3].X, LocalPoints[3].Y);
    }
    GL.End();
    GL.Disable(EnableCap.Texture2D);

    float wid = Stroke.Width;
    Color col = Stroke.Color;

    if (wid > 0)
    {
        for (int i = 0; i < LocalPoints.Count; i++)
        {
            int j = (i + 1) % LocalPoints.Count;
            GMapControl.line(LocalPoints[i].X, LocalPoints[i].Y, LocalPoints[j].X, LocalPoints[j].Y, wid, col);
        }
    }
}

Answers at Perspective correct texturing of trapezoid in OpenGL ES 2.0 http://www.reedbeta.com/blog/quadrilateral-interpolation-part-1/ https://gamedev.stackexchange.com/questions/68021/how-can-i-draw-a-perspective-correct-quad How to texture a random convex quad in openGL wasn't helpful...

Answer 1

I found solution with perspective correction for Quad

public override void OnRender()
{
    if (LocalPoints.Count == 4 && !targetPosition.IsEmpty)
    {
        if (!backgroundColor.HasValue)
            backgroundColor = new Pen(Fill).Color;
        GL.Color4(backgroundColor.Value);

        lock (bitmapSync)
        {
            if (bitmap != null)
                createTexture();
        }

        GL.Enable(EnableCap.Texture2D);
        GL.BindTexture(TextureTarget.Texture2D, texture);

        // center point
        GPoint localTargetPosition = MainForm.instance.gMapControl.FromLatLngToLocalWithOffset(targetPosition);
        // determines distances to center for all vertexes
        double dUL = Common.distance(new double[] { LocalPoints[0].X, LocalPoints[0].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });
        double dUR = Common.distance(new double[] { LocalPoints[1].X, LocalPoints[1].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });
        double dLR = Common.distance(new double[] { LocalPoints[2].X, LocalPoints[2].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });
        double dLL = Common.distance(new double[] { LocalPoints[3].X, LocalPoints[3].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });

        var texCoords = new[]
        {
            new Vector4(0, 0, 1, 1),
            new Vector4(1, 0, 1, 1),
            new Vector4(1, 1, 1, 1),
            new Vector4(0, 1, 1, 1)
        };

        texCoords[0] *= (float)((dUL + dLR) / dLR);
        texCoords[1] *= (float)((dUR + dLL) / dLL);
        texCoords[2] *= (float)((dLR + dUL) / dUL);
        texCoords[3] *= (float)((dLL + dUR) / dUR);

        GL.Begin(PrimitiveType.Quads);
        {
            //GL.TexCoord2(0, 0); //UL  LocalPoints[0] gimbalUL
            //GL.TexCoord2(1, 0); //UR  LocalPoints[1] gimbalUR
            //GL.TexCoord2(1, 1); //LR  LocalPoints[2] gimbalLR
            //GL.TexCoord2(0, 1); //LL  LocalPoints[3] gimbalLL
            GL.TexCoord4(texCoords[0]); GL.Vertex4(LocalPoints[0].X, LocalPoints[0].Y, 1, 1);
            GL.TexCoord4(texCoords[1]); GL.Vertex4(LocalPoints[1].X, LocalPoints[1].Y, 1, 1);
            GL.TexCoord4(texCoords[2]); GL.Vertex4(LocalPoints[2].X, LocalPoints[2].Y, 1, 1);
            GL.TexCoord4(texCoords[3]); GL.Vertex4(LocalPoints[3].X, LocalPoints[3].Y, 1, 1);
        }

        GL.End();
        GL.Disable(EnableCap.Texture2D);

        float wid = Stroke.Width;
        Color col = Stroke.Color;

        if (wid > 0)
        {
            for (int i = 0; i < LocalPoints.Count; i++)
            {
                int j = (i + 1) % LocalPoints.Count;
                GMapControl.line(LocalPoints[i].X, LocalPoints[i].Y, LocalPoints[j].X, LocalPoints[j].Y, wid, col);
            }
        }
    }
    else
    {
        base.OnRender();
    }

}