There is a tool on PS called magic wand tool. After opening the picture, click on the white place with the magic wand tool. (Note that the tolerance in the upper left corner should not be too large, and there is a "continuous" after the tolerance. Don't tick! ! ! ), the magic wand selects all white areas, right-click to select deselect, that is, select the seal, and then copy. Then open the picture you want to stamp in PS and paste the stamp.

If I get this for you and upload it again, neither jpeg\png nor bmp will show that transparency is white. Only psd format can keep transparency.

If you save the stamp with psd, the rest are transparent. After selecting all the white areas, you can press DEL to delete them. If you think you have deleted too much, it is because your tolerance is too small. )

Try it yourself. Or leave an email and I'll send you PSD pictures.