QuickFont.QBitmap.DownScale32 C# (CSharp) Method

        public void DownScale32(int newWidth, int newHeight)
        {
            

            QBitmap newBitmap = new QBitmap(new Bitmap(newWidth, newHeight, bitmap.PixelFormat));

            if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
                throw new Exception("DownsScale32 only works on 32 bit images");

            float xscale = (float)bitmapData.Width / newWidth;
            float yscale = (float)bitmapData.Height / newHeight;

            byte r = 0, g = 0, b = 0, a = 0;
            float summedR = 0f;
            float summedG = 0f;
            float summedB = 0f;
            float summedA = 0f;

            int left, right, top, bottom;  //the area of old pixels covered by the new bitmap


            float targetStartX, targetEndX;
            float targetStartY, targetEndY;

            float leftF, rightF, topF, bottomF; //edges of new pixel in old pixel coords
            float weight;
            float weightScale = xscale * yscale;
            float totalColourWeight = 0f;

            for (int m = 0; m < newHeight; m++)
            {
                for (int n = 0; n < newWidth; n++)
                {

                    leftF = n * xscale;
                    rightF = (n + 1) * xscale;

                    topF = m * yscale;
                    bottomF = (m + 1) * yscale;

                    left = (int)leftF;
                    right = (int)rightF;

                    top = (int)topF;
                    bottom = (int)bottomF;

                    if (left < 0) left = 0;
                    if (top < 0) top = 0;
                    if (right >= bitmapData.Width) right = bitmapData.Width - 1;
                    if (bottom >= bitmapData.Height) bottom = bitmapData.Height - 1;

                    summedR = 0f;
                    summedG = 0f;
                    summedB = 0f;
                    summedA = 0f;
                    totalColourWeight = 0f;

                    for (int j = top; j <= bottom; j++)
                    {
                        for (int i = left; i <= right; i++)
                        {
                            targetStartX = Math.Max(leftF, i);
                            targetEndX = Math.Min(rightF, i + 1);

                            targetStartY = Math.Max(topF, j);
                            targetEndY = Math.Min(bottomF, j + 1);

                            weight = (targetEndX - targetStartX) * (targetEndY - targetStartY);

                            GetPixel32(i, j, ref r, ref g, ref b, ref a);

                            summedA += weight * a;

                            if (a != 0)
                            {
                                summedR += weight * r;
                                summedG += weight * g;
                                summedB += weight * b;
                                totalColourWeight += weight;
                            }

                        }
                    }

                    summedR /= totalColourWeight;
                    summedG /= totalColourWeight;
                    summedB /= totalColourWeight;
                    summedA /= weightScale;

                    if (summedR < 0) summedR = 0f;
                    if (summedG < 0) summedG = 0f;
                    if (summedB < 0) summedB = 0f;
                    if (summedA < 0) summedA = 0f;

                    if (summedR >= 256) summedR = 255;
                    if (summedG >= 256) summedG = 255;
                    if (summedB >= 256) summedB = 255;
                    if (summedA >= 256) summedA = 255;

                    newBitmap.PutPixel32(n, m, (byte)summedR, (byte)summedG, (byte)summedB, (byte)summedA);
                }

            }
            

            this.Free();
            
            this.bitmap = newBitmap.bitmap;
            this.bitmapData = newBitmap.bitmapData;
        }