I m using the following code to resize a bitmap using GDI+ in C. I m getting gray values for the top edge even for images where that area should be white. The problem disappears when the interpolation is nearest neighbor. However, I tried bicubic interpolation with ImageMagick and it seems fine. Any limitations problems I should know of? Is my method of scaling wrong somehow? Thanks!
(inputs: destSize : destination Gdiplus::Size m_pBitmap : source bitmap)
Rect destRect(Point(0,0), destSize);
Bitmap *pBitmap24BPP = new Bitmap(destSize.Width, destSize.Height, PixelFormat24bppRGB);
pBitmap24BPP->SetResolution(m_pBitmap->GetHorizontalResolution(), m_pBitmap->GetVerticalResolution());
Graphics *pGraphics = Graphics::FromImage(pBitmap24BPP);
pGraphics->SetInterpolationMode(InterpolationModeHighQualityBilinear);
pGraphics->DrawImage(m_pBitmap, destRect, 0, 0, m_pBitmap->GetWidth(), m_pBitmap->GetHeight() , UnitPixel, NULL);
//cleanup