I was wondering how I can do this type of optical illusion. Is it done manually or is there a quicker way to do it. Thanks ahead of time.
Simulate the old bw photo printing system. There dot sizes or line widths are modulated by local greyshades.
- have a bw photo as a layer
- have a pattern of black lines or dots on white. The pattern is your major line art and the printing raster at the same time. The illusion is the simulated greyshades.
- blur the pattern. A slight zone of black and white should be left.
- adjust the curves to get uniform shift from white to black in the blurred pattern
- copy the blurred pattern to the layer mask of the photo, invert the mask!
- insert a white background
- make a safety copy of everything to be able to readjust and try again
- merge the background and the masked photo
- choose proper foreground and background colors in the tool palette; black and white are good.
- go to image adjustment "Treshold"
- adjust the treshold for your taste
Overlay your original pattern to make the line art dominant.
Here are a couple of examples. The line art is a bunch of horizontal straight lines. First a noisy smartphone photo is hidden into the "art"
In this example a second piece of art is hidden into the same horizontal line art: