package main import ( "flag" "fmt" "image" "image/draw" _ "image/jpeg" "image/png" "log" "os" "rescribe.xyz/preproc/integralimg" ) const usage = `Usage: splittable [-t thresh] [-w winsize] inimg outbase splittable is an experimental program to split a table into individual cells suitable for OCR. It does this by detecting lines. At present it just detects vertical lines and outputs images for each section between those lines. ` // 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() } // findbestvline goes through every vertical line from x to x+w to // find the one with the lowest proportion of black pixels. func findbestvline(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 } // findvlines finds vertical lines, returning an array of x coordinates // for each line. It works by moving a window of wsize across the image, // marking each place where there is a higher proportion of black pixels // than thresh. func findvlines(img integralimg.I, wsize int, thresh float64) []int { maxx := len(img[0]) - 1 var lines []int for x := 0; x < maxx-wsize; x+=wsize { if proportion(img, x, wsize) >= thresh { l := findbestvline(img, x, wsize) lines = append(lines, l) } } return lines } func drawsection(img *image.Gray, x1 int, x2 int) *image.Gray { b := img.Bounds() width := x2-x1 new := image.NewGray(image.Rect(0, b.Min.Y, width, b.Max.Y)) for x := 0; x < width; x++ { for y := b.Min.Y; y < b.Max.Y; y++ { new.SetGray(x, y, img.GrayAt(x1 + x, y)) } } return new } func main() { flag.Usage = func() { fmt.Fprintf(flag.CommandLine.Output(), usage) flag.PrintDefaults() } thresh := flag.Float64("t", 0.85, "Threshold for the proportion of black pixels below which a window is determined to be a line. Higher means fewer lines will be found.") wsize := flag.Int("w", 1, "Window size for mask finding algorithm.") flag.Parse() if flag.NArg() < 2 { flag.Usage() os.Exit(1) } f, err := os.Open(flag.Arg(0)) defer f.Close() if err != nil { log.Fatalf("Could not open file %s: %v\n", flag.Arg(0), err) } img, _, err := image.Decode(f) if err != nil { log.Fatalf("Could not decode image: %v\n", err) } b := img.Bounds() gray := image.NewGray(image.Rect(0, 0, b.Dx(), b.Dy())) draw.Draw(gray, b, img, b.Min, draw.Src) integral := integralimg.ToIntegralImg(gray) vlines := findvlines(integral, *wsize, *thresh) for i, v := range vlines { fmt.Printf("line detected at x=%d\n", v) if i+1 >= len(vlines) { break } section := drawsection(gray, v, vlines[i+1]) fn := fmt.Sprintf("%s-%d.png", flag.Arg(1), v) f, err = os.Create(fn) if err != nil { log.Fatalf("Could not create file %s: %v\n", fn, err) } defer f.Close() err := png.Encode(f, section) if err != nil { log.Fatalf("Could not encode image %s: %v\n", fn, err) } } // TODO: find horizontal lines too // TODO: do rotation // TODO: output table cells // TODO: potentially send cells straight to tesseract }