i want invert , gray scale image. here original image:
here final result want achieve (produced paint.net):
however using (basic?) java code found on internet, picture below: 
here code used:
private static final byte[] inverttable; static { inverttable = new byte[256]; (int = 0; < 256; i++) { inverttable[i] = (byte) (255 - i); } } private static bufferedimage grayscale(bufferedimage source) { colorconvertop grayscale = new colorconvertop(colorspace.getinstance(colorspace.cs_gray), null); return grayscale.filter(source,null); } private static bufferedimage invertimage(final bufferedimage src) { final int w = src.getwidth(); final int h = src.getheight(); final bufferedimage dst = new bufferedimage(w, h, bufferedimage.type_int_rgb); final bufferedimageop invertop = new lookupop(new bytelookuptable(0, inverttable), null); return invertop.filter(src, dst); } // ... bufferedimage sourceimage = ... bufferedimage convertedimage = grayscale(invertimage(sourceimage)); how can improve above code?
using imgproc , core, did
mat src = new mat(); mat gray = new mat(); src = highgui.imread("..."); imgproc.cvtcolor(src, gray, imgproc.color_bgr2gray); core.bitwise_not(gray, gray); highgui.imwrite("...", gray); and got closer, though not identical:
