A tutorial on some basic tools you can use with Inkscape, an open-source vector graphics editing software. The purpose of this is less about the actual project of posterizing an image, but more about the different ways you can edit/create anything on Inkscape. The project was just an easy way to demonstrate some of the useful tools I use most often, as an amateur.
Inkscape creates *.svg files, "scalable vector graphics." It's comparable to CorelDraw and Illustrator, and can save *.eps files which I'm told opens in CorelDraw (I've never used either).
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Step 1: Import and Trace Bitmap
Import an image by pasting it into Inkscape
Then, when the image is selected, go to Path > Trace Bitmap. This takes the image you imported and generates paths that we'll be working with. For posterizing a picture, Color Quantization OR Multiple Scans in color generally works, but play around to find what you're looking for. Guestimate how many colors/scans will be needed (the more scans, the more detail and closer the path is to the image).
After clicking OK, the paths will be generated right ontop of the image. Using the selector tool, drag the paths away from the image.
Lastly, rightclick > Ungroup. The path is generated as a group of objects; each color is represented by a different object, and the objects are stacked on top of each other. You can regroup any set of paths by going to the Object menu.
Step 2: Tweaking Paths
After ungrouping, we can now edit each object (*Note, I use object and layer interchangeably, b/c with traced bitmaps they basically come out as scans stacked in layers. Objects have paths, paths are objects, also practically interchangeable.)
For example, cutting out a large portion. In the peach colored layer, we want to get rid of the excess above her head. After pulling out the desired layer with the normal selector (usually with traced images it's a little tricky), use the path editor and drag a rectangle over the portion you want to delete. Delete, and we'll smooth out the change. Using the path editor, drag either the edge of the object itself or the nodes/node "arms" to tweak the shape. You can also click individual nodes to delete them. Shift allows you to select multiple nodes at once.
Step 3: Splitting Paths
To split a path, the easiest way is to use the calligraphy marker and draw a line across where you want to split the path. Technically speaking this is just deleting the "bridge" between two ends of a path, but it works to split something as well. Draw where you want to delete select both the drawn line and path, then Path > Difference.
Step 4: Tweak!
Using those steps, you can significantly simplify or edit an avatar.
-Get rid of incorrectly colored backgrounds, or just unnecessary layers by dragging them away
- Get rid of details by deleting nodes
- Simplify paths with Crtl + L
Step 5: Save and Export
Saving will save the file as *.svg, or you can choose another vector format. You can change Document size by going to File > Doc Properties.
To export it as an image file, go to File > Export Bitmap
If you export an image as PNG, you may want to create a white object with the Rectangle tool and changing its color to white, depending on if you need a transparent back or not.