First right click on this image and save it on your desktop and open it on Photoshop
Duplicate the current layer by pressing CTRL+J then go to Image>Adjustment>Posterize. Type 7 in the levels input box.
The posterized layer will serve as a guide to the shades of color that we need to trace. The higher the level of posterizing you use the more realistic your vector will look but it will also be more difficult to work on.
Now press F to go into fullscreen mode, this will make tracing shapes easier. Zoom in at around 300% using the zoom tool, then hold down the space bar (your cursor will change to a hand) click and drag the image so that you are looking at the part of the picture same as below.
Click on the background layer to activate it then press P to select the pen tool, using the above image as a reference click on the starting point. You will notice that a new layer is created named “Shape 1″ on the Layers Palette. That is normal and this simply means that we are working on a vector shape. Follow the guide below to start tracing the outline of the skin of the model in the picture.
You may notice that I intentionally placed a node outside the picture, you don’t have to worry about this because any nodes outside the picture will not show and will not affect the vector. Also, in case you made a mistake or the curved path did not fit well you can hit CTRL+Z to undo. You can also edit any past node by holding the CTRL button and drag any node that you want to edit.
Continue tracing the shape until you have something like the image below:
What we are doing here is to trace first all the skin parts. Finish tracing the belly and the leg part, don’t forget to close you shape. Click on the “add to shape area” on the shape options.
What this does is to add the next vector shape in the same layer. This way we can keep our layer organized and easier to edit in case we need to come back and correct something. Continue tracing the other skin shapes so you may end up with something like this:
And this is what your layers palette should look like:
The top layer is your posterized picture, the middle layer is the shape layer which ou are working on and the bottom layer is the original picture. You can toggle on and off a layer by clicking on the layer visibility toggle icon. You can turn off the top layer so you can see how are you doing with your vector. Double click the box found on the left side of you shape layer to change its color. Select a color that is close to the primary skin color of our model (I used #F7CDB8). This will be the basic skin color of our vector, you will add highlights and shadows later to this to finish the vector skin.
Here’s what your current work should look like with the posterized layer turned off: