One way would be to actually convert it to a vector image. Using Inkscape, follow these steps:
- Create a new Inkscape document.
- Select
File
->Import
and select your current file (just link to it when asked). - Resize the document to fit it:
- Open the document properties Shift + Ctrl + D
- Click the
Resize Document to Contents
button.
- Trace the bitmap image with the correct amount of precision to eliminate the speckles.
- Open the trace dialog: Shift + Alt + B
- Select
Grays
underMultiple Scans
on the Trace Bitmap dialog. Use 2 for the color and scan count (although I'm not certain the later matters). - In the options tab of that same dialog make sure that all options are selected and the values read
10, 1.00, 1.00
down the column.
- Press OK once everything looks good.
- At this point, you can remove the original PNG link that was imported into the file.
- If you'd rather have this be PNG format, just export it as a PNG again.
The finished PNG (although, if it were me, I'd just follow the steps above to get it into SVG format and use InkScape to edit it):