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// Copyright 2020 Nick White.
// Use of this source code is governed by the GPLv3
// license that can be found in the LICENSE file.
// pggraph creates a graph showing the proportion of black pixels
// for slices through an image. This is useful to determine
// appropriate parameters to pass to the wipe functions in this
// module.
package main
import (
"flag"
"fmt"
"image"
"image/draw"
_ "image/jpeg"
_ "image/png"
"io"
"log"
"os"
"sort"
chart "github.com/wcharczuk/go-chart"
"rescribe.xyz/integralimg"
)
const usage = `Usage: pggraph [-vertical] [-width] inimg graphname
Creates a graph showing the proportion of black pixels
for slices through an image. This is useful to determine
appropriate parameters to pass to the wipe functions in
this module.
`
const middlePercent = 20
const numTicks = 30
// sideways flips an image sideways
func sideways(img *image.Gray) *image.Gray {
b := img.Bounds()
newb := image.Rect(b.Min.Y, b.Min.X, b.Max.Y, b.Max.X)
new := image.NewGray(newb)
for x := b.Min.X; x < b.Max.X; x++ {
for y := b.Min.Y; y < b.Max.Y; y++ {
new.SetGray(y, x, img.GrayAt(x, y))
}
}
return new
}
func graph(title string, points map[int]float64, w io.Writer) error {
var xvals, yvals []float64
var xs []int
var midxvals, midyvals []float64
var midxs []int
if len(points) < 2 {
return fmt.Errorf("Not enough points to graph, only %d\n", len(points))
}
for x, _ := range points {
xs = append(xs, x)
}
sort.Ints(xs)
for _, x := range xs {
xvals = append(xvals, float64(x))
yvals = append(yvals, points[x])
}
mainSeries := chart.ContinuousSeries{
Style: chart.Style{
StrokeColor: chart.ColorBlue,
FillColor: chart.ColorAlternateBlue,
},
XValues: xvals,
YValues: yvals,
}
numAroundMiddle := int(middlePercent / 2 * float64(len(xs)) / float64(100))
if numAroundMiddle > 1 {
for i := (len(xs) / 2) - numAroundMiddle; i < (len(xs)/2)+numAroundMiddle; i++ {
midxs = append(midxs, xs[i])
}
} else {
midxs = xs
}
for _, x := range midxs {
midxvals = append(midxvals, float64(x))
midyvals = append(midyvals, points[x])
}
middleSeries := chart.ContinuousSeries{
XValues: midxvals,
YValues: midyvals,
}
minSeries := &chart.MinSeries{
Style: chart.Style{
StrokeColor: chart.ColorAlternateGray,
StrokeDashArray: []float64{5.0, 5.0},
},
InnerSeries: middleSeries,
}
maxSeries := &chart.MaxSeries{
Style: chart.Style{
StrokeColor: chart.ColorAlternateGray,
StrokeDashArray: []float64{5.0, 5.0},
},
InnerSeries: middleSeries,
}
var ticks []chart.Tick
var tickEvery = xs[len(xs)-1] / numTicks
for i := 0; i < xs[len(xs)-1]; i += tickEvery {
ticks = append(ticks, chart.Tick{float64(i), fmt.Sprintf("%d", i)})
}
lastx := xs[len(xs)-1]
ticks[len(ticks)-1] = chart.Tick{float64(lastx), fmt.Sprintf("%d", lastx)}
graph := chart.Chart{
Title: title,
Width: 1920,
Height: 800,
XAxis: chart.XAxis{
Name: "Pixel number",
Ticks: ticks,
},
YAxis: chart.YAxis{
Name: "Proportion of black pixels",
},
Series: []chart.Series{
mainSeries,
minSeries,
maxSeries,
chart.LastValueAnnotationSeries(minSeries),
chart.LastValueAnnotationSeries(maxSeries),
},
}
return graph.Render(chart.PNG, w)
}
func main() {
flag.Usage = func() {
fmt.Fprintf(flag.CommandLine.Output(), usage)
flag.PrintDefaults()
}
vertical := flag.Bool("vertical", false, "Slice image vertically (from top to bottom) rather than horizontally")
width := flag.Int("width", 5, "Width of slice in pixels (height if in vertical mode)")
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()
if *vertical {
gray := image.NewGray(b)
draw.Draw(gray, b, img, b.Min, draw.Src)
img = sideways(gray)
b = img.Bounds()
}
intImg := integralimg.NewImage(b)
draw.Draw(intImg, b, img, b.Min, draw.Src)
points := make(map[int]float64)
maxx := b.Dx() - 1
for x := 0; x+*width < maxx; x += *width {
w := intImg.GetVerticalWindow(x, *width)
points[x] = w.Proportion()
}
f, err = os.Create(flag.Arg(1))
defer f.Close()
if err != nil {
log.Fatalf("Could not create file %s: %v\n", flag.Arg(1), err)
}
title := fmt.Sprintf("Proportion of black pixels over %s (width %d)", flag.Arg(0), *width)
if *vertical {
title += " (vertical)"
}
err = graph(title, points, f)
if err != nil {
log.Fatalf("Could not create graph: %v\n", err)
}
}
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