John Drake

I wrote this C# code for Paint.NET, an open source image editing program.

It applies this water reflection effect to the lower half of the currently open image. It's somewhat like a Photoshop "filter."

Code:

float RippleFrequency = 10f; //0+
float RippleAmplitude = 100; //0 to 100 (Percent)
float RippleSizeChange = 1; //0+

float anglecoefficient;
float cosinecoefficient;
float sizechange;

float yadj;
float halfy;
float maxy;
float yoff;
float height;

ColorBgra color;

void Render(Surface dst, Surface src, Rectangle rect)
{
    maxy = (dst.Height - 1f) / 2;
    halfy = maxy / 2f;
    
    anglecoefficient = RippleFrequency / 1000;
    cosinecoefficient = RippleAmplitude * halfy / 100;
    sizechange = RippleSizeChange / 100;
    
    for(float y = rect.Top; y < rect.Bottom; y++)
    {
        for (float x = rect.Left; x < rect.Right; x++)
        {
            yoff = y - maxy;
            if (y >= maxy)
            {
                yadj = (int)(cosinecoefficient * Math.Cos(yoff * anglecoefficient * sizechange * (maxy * 2 - yoff))) + halfy;
            color.A = (byte)(256 - (yoff / maxy) * 256f);
            }
            else
            {
                yadj = y;
            }
                color = src.GetBilinearSample(x, yadj, true);

dst[(int)x, (int)y] = color;
        }
    }
}