package preproc // TODO: add minimum size variable (default ~30%?) // TODO: switch to an interface rather than integralimg.I import ( "errors" "fmt" "image" "image/color" "image/draw" _ "image/jpeg" "image/png" "os" "rescribe.xyz/preproc/integralimg" ) // returns the proportion of the given window that is black pixels func proportion(i integralimg.I, x int, size int) float64 { w := i.GetVerticalWindow(x, size) return w.Proportion() } // findbestedge goes through every vertical line from x to x+w to // find the one with the lowest proportion of black pixels. func findbestedge(img integralimg.I, x int, w int) int { var bestx int var best float64 if w == 1 { return x } right := x + w for ; x < right; x++ { prop := proportion(img, x, 1) if prop > best { best = prop bestx = x } } return bestx } // findedges finds the edges of the main content, by moving a window of wsize // from near the middle of the image to the left and right, stopping when it reaches // a point at which there is a lower proportion of black pixels than thresh. func findedges(img integralimg.I, wsize int, thresh float64) (int, int) { maxx := len(img[0]) - 1 var lowedge, highedge int = 0, maxx // don't start at the middle, as this will fail for 2 column layouts, // start 10% left or right of the middle notcentre := maxx / 10 for x := maxx/2 + notcentre; x < maxx-wsize; x++ { if proportion(img, x, wsize) <= thresh { highedge = findbestedge(img, x, wsize) break } } for x := maxx/2 - notcentre; x > 0; x-- { if proportion(img, x, wsize) <= thresh { lowedge = findbestedge(img, x, wsize) break } } return lowedge, highedge } // wipesides fills the sections of image not within the boundaries // of lowedge and highedge with white func wipesides(img *image.Gray, lowedge int, highedge int) *image.Gray { b := img.Bounds() new := image.NewGray(b) // set left edge white for x := b.Min.X; x < lowedge; x++ { for y := b.Min.Y; y < b.Max.Y; y++ { new.SetGray(x, y, color.Gray{255}) } } // copy middle for x := lowedge; x < highedge; x++ { for y := b.Min.Y; y < b.Max.Y; y++ { new.SetGray(x, y, img.GrayAt(x, y)) } } // set right edge white for x := highedge; x < b.Max.X; x++ { for y := b.Min.Y; y < b.Max.Y; y++ { new.SetGray(x, y, color.Gray{255}) } } return new } // toonarrow checks whether the area between lowedge and highedge is // less than min % of the total image width func toonarrow(img *image.Gray, lowedge int, highedge int, min int) bool { b := img.Bounds() imgw := b.Max.X - b.Min.X wipew := highedge - lowedge if float64(wipew)/float64(imgw)*100 < float64(min) { return true } return false } // Wipe fills the sections of image which fall outside the content // area with white, providing the content area is above min % func Wipe(img *image.Gray, wsize int, thresh float64, min int) *image.Gray { integral := integralimg.ToIntegralImg(img) lowedge, highedge := findedges(integral, wsize, thresh) if toonarrow(img, lowedge, highedge, min) { return img } return wipesides(img, lowedge, highedge) } // WipeFile wipes an image file, filling the sections of the image // which fall outside the content area with white, providing the // content area is above min %. // inPath: path of the input image. // outPath: path to save the output image. // wsize: window size for wipe algorithm. // thresh: threshold for wipe algorithm. // min: minimum % of content area width to consider valid. func WipeFile(inPath string, outPath string, wsize int, thresh float64, min int) error { f, err := os.Open(inPath) defer f.Close() if err != nil { return errors.New(fmt.Sprintf("Could not open file %s: %v", inPath, err)) } img, _, err := image.Decode(f) if err != nil { return errors.New(fmt.Sprintf("Could not decode image: %v", err)) } b := img.Bounds() gray := image.NewGray(image.Rect(0, 0, b.Dx(), b.Dy())) draw.Draw(gray, b, img, b.Min, draw.Src) clean := Wipe(gray, wsize, thresh, min) f, err = os.Create(outPath) if err != nil { return errors.New(fmt.Sprintf("Could not create file %s: %v", outPath, err)) } defer f.Close() err = png.Encode(f, clean) if err != nil { return errors.New(fmt.Sprintf("Could not encode image: %v", err)) } return nil }