/// <summary>
/// Scale the bitmap, keeping aspect ratio, but the canvas will always have the specified size.
/// </summary>
/// <param name="sourceImage">Image to scale</param>
/// <param name="maintainAspectRatio">true to maintain the aspect ratio</param>
/// <param name="canvasUseNewSize">Makes the image maintain aspect ratio, but the canvas get's the specified size</param>
/// <param name="backgroundColor">The color to fill with, or Color.Empty to take the default depending on the pixel format</param>
/// <param name="newWidth">new width</param>
/// <param name="newHeight">new height</param>
/// <param name="matrix">Matrix</param>
/// <param name="interpolationMode">InterpolationMode</param>
/// <returns>a new bitmap with the specified size, the source-Image scaled to fit with aspect ratio locked</returns>
public static Bitmap Resize(this Image sourceImage, bool maintainAspectRatio, bool canvasUseNewSize, Color backgroundColor, int newWidth, int newHeight, Matrix matrix, InterpolationMode interpolationMode = InterpolationMode.HighQualityBicubic)
{
var destX = 0;
var destY = 0;
var nPercentW = newWidth / (float)sourceImage.Width;
var nPercentH = newHeight / (float)sourceImage.Height;
if (maintainAspectRatio)
{
if ((int)nPercentW == 1 || (int)nPercentH != 0 && nPercentH < nPercentW)
{
nPercentW = nPercentH;
if (canvasUseNewSize)
{
destX = Math.Max(0, Convert.ToInt32((newWidth - sourceImage.Width * nPercentW) / 2));
}
}
else
{
nPercentH = nPercentW;
if (canvasUseNewSize)
{
destY = Math.Max(0, Convert.ToInt32((newHeight - sourceImage.Height * nPercentH) / 2));
}
}
}
var destWidth = (int)(sourceImage.Width * nPercentW);
var destHeight = (int)(sourceImage.Height * nPercentH);
if (newWidth == 0)
{
newWidth = destWidth;
}
if (newHeight == 0)
{
newHeight = destHeight;
}
Bitmap newBitmap;
if (maintainAspectRatio && canvasUseNewSize)
{
newBitmap = BitmapFactory.CreateEmpty(newWidth, newHeight, sourceImage.PixelFormat, backgroundColor, sourceImage.HorizontalResolution, sourceImage.VerticalResolution);
matrix?.Scale((float)newWidth / sourceImage.Width, (float)newHeight / sourceImage.Height, MatrixOrder.Append);
}
else
{
newBitmap = BitmapFactory.CreateEmpty(destWidth, destHeight, sourceImage.PixelFormat, backgroundColor, sourceImage.HorizontalResolution, sourceImage.VerticalResolution);
matrix?.Scale((float)destWidth / sourceImage.Width, (float)destHeight / sourceImage.Height, MatrixOrder.Append);
}
using (var graphics = Graphics.FromImage(newBitmap))
{
graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
graphics.SmoothingMode = SmoothingMode.HighQuality;
graphics.InterpolationMode = interpolationMode;
using (var wrapMode = new ImageAttributes())
{
wrapMode.SetWrapMode(WrapMode.TileFlipXY);
graphics.DrawImage(sourceImage, new NativeRect(destX, destY, destWidth, destHeight), 0, 0, sourceImage.Width, sourceImage.Height, GraphicsUnit.Pixel, wrapMode);
}
}
return(newBitmap);
}
