Open ps and load a photo.

Copy the background layer into two new layers, named "Figure 1" and "Figure 2" respectively.

Click "Image-Adjustment-Decolorization" in turn, and the two layers of "Figure 1" and "Figure 2" will be decoloured respectively.

Select the layer "Figure 2" with the mouse, and click "Image-Adjust-Reverse" in turn to reverse the layer.

Double-click the "Figure 2" layer and change the blending mode to "Color Gradient".

Select the "Figure 2" layer and click "Filter-Blur-Gaussian Blur".

After Gaussian blur, the sketch effect comes out. You can choose to merge pictures or press and hold "alt+ctrl+shift+e" to stamp the layer.