/// <summary>
/// Read pixels in specified rect and get the VertexIds they represent.
/// </summary>
/// <param name="target"></param>
/// <returns></returns>
private static unsafe List <Tuple <Point, uint> > ReadPixels(Rectangle target)
{
var result = new List <Tuple <Point, uint> >();
// get coded color.
using (var codedColor = new UnmanagedArray <Pixel>(target.Width * target.Height))
{
OpenGL.ReadPixels(target.X, target.Y, target.Width, target.Height,
OpenGL.GL_RGBA, OpenGL.GL_UNSIGNED_BYTE, codedColor.Header);
var array = (Pixel *)codedColor.Header.ToPointer();
int index = 0;
var vertexIdList = new List <uint>();
for (int yOffset = target.Height - 1; yOffset >= 0; yOffset--)
{
for (int xOffset = 0; xOffset < target.Width; xOffset++)
{
Pixel pixel = array[index++];
// This is when (x, y) is not on background and some primitive is picked.
if (!pixel.IsWhite())
{
uint stageVertexId = pixel.ToStageVertexId();
if (!vertexIdList.Contains(stageVertexId))
{
result.Add(new Tuple <Point, uint>(
new Point(target.X + xOffset, target.Y + yOffset), stageVertexId));
vertexIdList.Add(stageVertexId);
}
}
}
}
}
return(result);
}
/// <summary>
/// Gets stage vertex id by color coded picking machanism.
/// Note: left bottom is(0, 0). This is different from Winform's left top being (0, 0).
/// </summary>
/// <param name="x">target pixel position(Left Down is (0, 0)).</param>
/// <param name="y">target pixel position(Left Down is (0, 0)).</param>
/// <returns></returns>
internal static unsafe uint ReadStageVertexId(int x, int y)
{
var array = new Pixel[1];
GCHandle pinned = GCHandle.Alloc(array, GCHandleType.Pinned);
IntPtr header = Marshal.UnsafeAddrOfPinnedArrayElement(array, 0);
// get coded color.
GL.Instance.ReadPixels(x, y, 1, 1, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, header);
pinned.Free();
Pixel pixel = array[0];
uint stageVertexId = pixel.IsWhite() ?
uint.MaxValue :
// This is when (x, y) is not on background and some primitive is picked.
pixel.ToStageVertexId();
return(stageVertexId);
}
/// <summary>
/// Read pixels in specified rect and get the VertexIds they represent.
/// </summary>
/// <param name="target"></param>
/// <returns></returns>
private static unsafe List <Tuple <Point, uint> > ReadPixels(Rectangle target)
{
// get coded color.
var codedColor = new Pixel[target.Width * target.Height];
{
GCHandle pinned = GCHandle.Alloc(codedColor, GCHandleType.Pinned);
IntPtr header = Marshal.UnsafeAddrOfPinnedArrayElement(codedColor, 0);
OpenGL.ReadPixels(target.X, target.Y, target.Width, target.Height,
OpenGL.GL_RGBA, OpenGL.GL_UNSIGNED_BYTE, header);
pinned.Free();
}
var result = new List <Tuple <Point, uint> >();
int index = 0;
var vertexIdList = new List <uint>();
for (int yOffset = target.Height - 1; yOffset >= 0; yOffset--)
{
for (int xOffset = 0; xOffset < target.Width; xOffset++)
{
Pixel pixel = codedColor[index++];
// This is when (x, y) is not on background and some primitive is picked.
if (!pixel.IsWhite())
{
uint stageVertexId = pixel.ToStageVertexId();
if (!vertexIdList.Contains(stageVertexId))
{
result.Add(new Tuple <Point, uint>(
new Point(target.X + xOffset, target.Y + yOffset), stageVertexId));
vertexIdList.Add(stageVertexId);
}
}
}
}
return(result);
}
