edge emboss fliph flipv gamma gray hue invert max value > 0 value (-100, 100) red green blue (-100, 500) hue (0-360) saturation (0-100) value (0-100) l for linear->sRGB or s for sRGB->linear value (-100, 100) x1 y1 x2 y2 (rectangle at (x1,y1) and (x2,y2) width height edge filter emboss filter flip horizontal flip vertical value (< 1 darken, > 1 lighten) grayscale image value (-180, 180) invert image local maximum size (odd positive integer) mean median min opacity pixelate resize resizefill resizefit rotate saturation sepia sigmoid sobel threshold transpose transverse unsharp local mean size (odd positive integer) local median size (odd positive integer) local minimum size (odd positive integer) value (0-100) pixels width height width height width height degrees counter-clockwise value (-100, 500) value (0-100) midpoint (0,1) factor (-10,10) sobel filter color threshold percentage (0-100) flip horizontally and rotate 90° counter-clockwise flip vertically and rotate 90° counter-clockwise sigma (> 0) amount (0.5, 1.5) threshold (0, 0.05)