Hey, and thanks for this great libray,

I'm maintaining Hugo and have been looking for a library like this to integrate into the image processing. But that would need to be open source. Could you add a suitable license to this repository?

Thanks!

src image

got svg

I have a compatibility problem with the go modules:

filters/svgtrace.go:12:2: unknown import path "github.com/dennwc/gotrace": unzip /home/xxx/go/pkg/mod/cache/download/github.com/dennwc/gotrace/@v/v0.0.0-20151111213338-0306f421d687.zip: malformed file path "aux.go": disallowed path element "aux.go"

as microsoft says:

• Do not use the following reserved names for the name of a file:
  CON, PRN, AUX, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9. Also avoid these names followed immediately by an extension; for example, NUL.txt is not recommended. For more information, see Namespaces.

it should be enough to rename the file aux.go

see here for further details

This is in fact same bug as reported in #4. It is caused when image has background (e.g. "white" in #4) as solid and "black" as transparent. Then trace code properly creates rectangle with holes as child elements. But as WriteSvg() function completely ignores child paths, result is SVG with just single black rectangle.

Same problem is valid even when background is transparent for objects with holes.
See this example (face is most visible missing feature):

Hi, thanks a lot for your work on this package.

I tried to reproduce tracing the sample image from the readme.
The outlines look jagged and it seems that there are no holes at all in the image.

I tried using both gotrace.Trace and gotraceb.Trace
I'm on Ubuntu 22.04 using WLS2 from a Windows 11 host and I tried both go1.19.3 and go1.10.

When I use the potrace command line tool, the output looks fine.

package main

import (
	"fmt"
	"image"
	"image/color"
	_ "image/png"
	"os"

	"github.com/dennwc/gotrace"
	gotraceb "github.com/dennwc/gotrace/bindings"
)

func main() {
	imgPath := "/home/jakob/tmp/potrace/stanford-orig2.png"

	rdr, err := os.Open(imgPath)
	check(err)
	defer rdr.Close()

	img, _, err := image.Decode(rdr)
	check(err)

	thresholdFunc := func(_, _ int, cl color.Color) bool {
		r, g, b, _ := cl.RGBA()
		return r+g+b < 128
	}
	bm := gotrace.NewBitmapFromImage(img, thresholdFunc) 

	paths, err := gotrace.Trace(bm, nil)
	//paths, err := gotraceb.Trace(bm, nil)

	f, err := os.Create("/home/jakob/tmp/trace.svg")
	check(err)
	defer f.Close()

	gotrace.WriteSvg(f, image.Rect(0, 0, img.Bounds().Dx(), img.Bounds().Dy()), paths, "red")
}

func check(err error) {
	if err != nil {
		fmt.Println(err)
		panic(err)
	}
}