It was quite by accident that I was able to achieve this edit in iColorama. I will tell you what I did to get here but I'm afraid I can't tell you why or how some of it worked because parts of the app are confusing to me. I will eventually know it inside out, but for now....
You shouldn't need to do this, but you can if you want. To get rid of the 'canvas' texture I chose Style>Coherence>Preset 1. Click Apply.
Next choose Brush>Bristle. You have to wait a few seconds for your canvas to turn 'white' (completely blank) then you begin to 'paint' back in the part of the photo you want revealed. I left it on Preset 1 but you can try some of the others. Be warned, some will smear the paint. (I didn't change the brush)
When you're satisfied (there is only one undo) click the Apply check mark.
Staying in the Brush Module, choose Paint. Pick a brush that is the pattern you would like to 'erase' your art. In brushes click on 'single' to get the choices of that particular brush category. Adjust the size. Then 'stamp' at the outer edge to get 'edge' patterns. Remember there is only one undo.
However, once you've clicked Apply you can go to Steps in the upper left corner to back up to a previously saved step.
Next Choose Style>Edges, change the blend mode to Multiply. You can choose a different preset or change the size of the edge line width.
BEFORE you click apply... Click the Zoom/Move tool. A blue line appears around the whole screen to show it is active. Move your photo to the left and zoom in so you can see one side of your edges. touch the Zoom/Move again to deactivate it.
Touch the Brush/Mask. It has a red line to show it's active. Now 'erase' any edge lines you wish. I left just the ones around the white filagrees. If you change your sketch layer back to normal it's easier to see where you've erased it. Then change back to multiply.
NOW click apply.
If you'd like to play with a little color change, choose Preset>Colors2. Choose a preset, change the blend mode, lots of options for some different toning.
Save your file, don't close the app. Go to Steps, chose the first step to get back to the original photo. (if you didn't do Coherence, if you did you may want to choose that one.)
Next under Style>Edges. Choose a preset that shows good outlines. This will only be for reference for drawing purposes unless you want to use it for your sketch layer. Save to camera roll.
Next up, Procreate!
For great tutorials on how to get started with Procreate checkout The Digital Painter's YouTube. He has three great tutorials.
Here are what my layers looked like.
Initially I reduced the opacity of the sketch layer to use it for a guide to sketch by. Be sure to create a new layer to sketch on. The first ink layer was black. Then I decided a little white ink might look nice. So that went on a separate layer.
After I thought I was finished, I changed the original sketch layer to 15% opacity and blend mode soft light to brighten up the whole piece.