How do I flip an image across the Y-axis?

I have an image which I want to create a PDF from but mirrored, so it is flipped across the Y axis.


using (PDFDoc doc = new PDFDoc())
using (ElementBuilder bld = new ElementBuilder())
using (ElementWriter writer = new ElementWriter())
	Image img = Image.Create(doc, pathToImage);
	int imgW = img.GetImageWidth();
	int imgH = img.GetImageHeight();
	var mtx = new Matrix2D(imgW, 0, 0, imgH, 0, 0);
	var mtxFlip = new Matrix2D(-1, 0, 0, 1, imgW, 0); // flip axis, and move image back to 1st quadrant (back into typical PDF page crop box area)
	mtx = mtxFlip * mtx;
	Element element = bld.CreateImage(img, mtx);
	Page page = doc.PageCreate(new Rect(0,0,imgW,imgH));
	writer.Begin(page, ElementWriter.WriteMode.e_overlay, false);