I am making some experiments and got stuck - can someone tell me how to “decolorize” an image in Photoshop, but leaving only the contour. Everything else should be white and not grayscaled. For example this type of image, it has a somewhat defined contour.

The reason - I am “theorizing” pattern designing. Meaning I am now experimenting only the theory (method). It is very unlikely that I will start to design (as I don’t really enjoy this), but the methodology is interesting to muse on.
So I came to a conclusion that actual quality designing means one thing - hardware. Not in the sense of computer hardware - but the good old paper, pencils, you know? Cross stitch software for now proves to be quite useless, at the methodology stage 1. It also proves to be useless at all other stages except the last one, when you may want to render your chart in an electronic form - for easier display of symbols, etc. But you also may not and can remain with the hand-drawn chart which you will scan, print, etc.
So far the conclusions I came to are:
1. You need a good deal of graph paper, or paper suitable for charts. Quality and in different sizes
2. You need a good quality printer. This is in case you can’t draw well by hand, but also why should you?
3. You can take a clip art image (like for example the one above), create a “clean” decolorized version of it and print it on the graph/chart paper.
The chart is done. If your paper, the image and the printer are all fine, you will easily see the blocks, curves and borders and easily understand where to stitch. Now for me neither my image and my printer are good, but still after printing on what I have and with what I have, I clearly saw that the image is coming out asolutely suitable.
So the stage one is complete. After that comes the most difficult part, actually the *real* designing stage - assigning colors. If your original clip art image already has colors, again half of the job is done, you know which colors and even shades go where. The other half is to have the ability to “translate” this into the chart by the use of DMC threads. Here the lecture stops, because this is already stage 2 and it is IMO in one’s personal skill, sense for color and ability to combine and produce the most “right” color effects. And a lot of work in stitching, restitching, adding, taking away, all until you are satisfied and can say “this is it”; and of course the “paperwork” of writing down your colors in the chart.
So these are my musings. Now back to my usual evening dutues.