Gimp Tips - Spray Painted Stencil

I saw a poster recently that was made to look like it was done with a stencil and spray paint. I though it looked kind of cool so tried to recreate the look in GIMP.

  1. Brooklyn Bridge This works best with a picture that begins with a lot of contrast. Outdoor scenes on bright days work well. I found this picture at morgueFile, a nice source for free stock photos.
  2. harsh black and white version Apply Colors|Threshold and play with the level to get roughly the look you want. Don't worry about the little speckly bits, we'll clean them up in a minute.
  3. enlarged to add a border around the image We need a little extra room to fit our stencil in, so use Image|Canvas Size to enlarge by about 15%. Click Center to keep your image in the middle. Then do Layer|Layer to Image Size to fill that new space.
  4. now it's all blurry Now we'll clean up those speckles. Filters|Blur|Gaussian Blur by 2 pixels.
  5. simpler pure black and white version Colors|Threshold again and keep it at 127 this time. This should give you a much cleaner version of your picture in black and white. Feel free to paint out an remaining spots or clean up important lines by hand.
  6. black and white with softer edges I think those jagged pixely edges still look harsh, so I soften them up with Filters|Blur|Gaussian Blur by 1 pixel. If your image has a high resolution, this won't matter.
  7. layers dialog with new black masked layer Copy the image. Add a new, black layer on top. Add a layer mask to that new top layer. Paste your image into the layer mask, and do Colors|Invert. This will give us a transparent copy of the image. We can play with the bottom layer and keep our original shape, too.
  8. Perlin noise added over the image Make a new channel and on it do Filters|Render|Clouds|Solid Noise at about 5 each way, setting detail to 1. This gives us a random area where paint will have gotten out under the edge of our stencil and will "spray" into the white area a bit.
  9. sharper edges on the noise we added Do Colors|Levels on the channel and set the input range to 130 to 160. This will make a sharper delineation between the spray areas and the clean areas.
  10. blurring within a squiggly selection Do Channel to Selection and hide the channel. Back on your original bottom layer Filters|Blur|Gaussian Blur by about 5% of your image size.
  11. final image with some overspray Do Filters|Noise|RGB Noise. Uncheck "Independent RGB" and set the levels at about 0.10. That will add some grainyness to the overspray, which is what spray paint looks like. For a high resolution image individual pixel noise won't be big enough to be visible, but it works fine for most web-scale images.