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c++windowscolorscolormatrix

Swap two colors using color matrix

How can I swap two colors using a color matrix? For instance swapping red and blue is easy. The matrix would look like:

0 0 1 0 0
0 1 0 0 0
1 0 0 0 0
0 0 0 1 0
0 0 0 0 1

So how can I swap any two colors in general? For example, there is Color1 with R1, G1, B1 and Color2 with R2, G2, B2.

EDIT: By swap I mean Color1 will translate into color2 and color2 will translate into color1. Looks like I need a reflection transformation. How to calculate it?

GIMP reference removed. Sorry for confusion.

Solution

  • I solved it by creating a reflection matrix via D3DXMatrixReflect using a plane that's perpendicular to the vector AB and intersects the midpoint of the AB.

    1. D3DXVECTOR3 AB( colorA.r-colorB.r, colorA.g-colorB.g, colorA.b-colorB.b );

    2. D3DXPLANE plane( AB.x, AB.y, AB.z, -AB.x*midpoint.x-AB.y*midpoint.y-AB.z*midpoint.z );

    3. D3DXMatrixReflect