How to make Lithophanes for the LED Holiday Litho-Lantern Bob Eaton (Festus440) Creating the lithophanes for the lantern is quite easy. You need to have some limited photo editing skill but if you're new to that these instructions will get you started. There are a number of software packages available to create the actual STL files including several slicer programs. I will show you how to do it with the Cura slicer program which is free and open source. Go to this site and download the version of Cura for your computer: http://software.ultimaker.com/ Install the software. The install wizard will ask for details about your printer. If you don't plan on using Cura to actually print the part, these setting won't be critical and you also won't need to install the Arduino drivers. You will also need some type of photo editing software. For this example I will use Gimp 2 which is also free and open source: http://www.gimp.org/ Note: I'm using the Windows versions of these software packages, but they are also available for Mac and Linux. Editing the Image I'll go through the steps I used to create the lithophane of my granddaughter. (I like this photo because she has this odd "what the heck is going on" look :-) Depending on the image, the exact procedure you use may need to be different but this should get you started. This is only one way to get the desired result. A high resolution is not needed. The actual image size in pixels we will use is 230 wide by 325 pixels high. The size of the finished lithophane should be 46mm wide by 65mm tall and 6mm thick. I chose the 6mm thickness because that is what I use when I cut lithophanes with my CNC mill. This thickness gives a good range of light to dark contrast. Since the overall size is small, it doesn't require much plastic or printing time.
Start the Gimp 2 program and load your image. For images of people, a close up will work best since the lithophane doesn't have as much resolution as a photo. You want an image that has a quite a bit of contrast. Also if you see any very small very bright spots, you may want remove them or reduce their brightness because these can bloom in the lithophane. (For example the glint in people's eyes.) I'm not going to cover how to do that here. Since her face in this photo is already centered about in the right place vertically, I will scale the whole image height to the final 325 pixel size in the vertical direction first. In Gimp, select "Image" and then "Scale Image" Make sure the small Lock symbol is "locked". And as I said in this case I'm going to make the entire image 325 pixels tall. Click scale. The result won't appear too much different just smaller and lower resolution. You can hold the CTRL key and use your mouse wheel to zoom back in on the image.
Now I need to crop the image so that the width is 230 pixels. From the menu click on the rectangle selection tool. Then draw a rectangle on the image. Grab the corners of the rectangle so that the top and bottom overlay the top and bottom edges of the image Next, on the left side of the screen type in the dimensions of the final image. Make sure that the drop down menu is set to pixels (px). You can click in the center of the selection box and move it around until everything is centered. When you are happy with the results click "Image" and then "crop to selection".
As a check, click on "Image" and then on "Image properties". Make sure that the size in pixels is 230 x 325 as shown here. There is one final editing step. In order to get a proper fit in the lantern you need to add a black spot in each corner of the image. The spots will be outside of the oval cutout in the lantern and be 6mm thick to hold it in place. To make the circular spots click on the circular selection tool. Place your cursor in a corner of the image and drag towards the center of the image to make small circle as shown. Size is not critical. You can click on the corners of the circle section and drag them around to get a rough circle.
We are going to fill the circle with black using the fill tool. Go ahead and click that. It looks like a bucket. Make sure the foreground color is black (where the arrow is pointing. If not, click on the upper color swatch and select pure black from the color palette (all the color values will be zero). Also make sure the settings in the tool options below the color swatch match what I have shown. When you are set, click in the center of the circular selection to fill it with black. Now repeat this process in all four corners of the image. (Hard to see the one in the upper right corner.)
Now we need to "Export" the image. Click on "File" and then "Export.." Type in the image name you want to use then add the ".jpg" extension to the name. A dialog for JPG options will appear now. You can crank up the quality to 100% Now we actually create the STL file for the lithophane. Start Cura. Click "File" and then "Load Model File..." Navigate to the place where you image was stored and select the JPG image you just created. The following dialog box will appear. Change the settings to the same as shown here. You don't need to change the "Depth". It should come out just slightly larger than 65mm. NOTE: Entering text into the "Width" text box is a little weird in this version. I found the easiest way to enter "46" was to enter the numbers backwards, type "6" and then "4".
When everything is set, click "OK" and the model will be created. The final step is to save the STL file. Click "File" and then save your creation with the file extension of ".stl". Print your lithophane using natural (white) PLA. I used a layer thickness of 0.15mm. Infill should be set to 100% The 6mm thickness also give the image an interesting 3D effect :-) The lithophane should be mounted in the lantern with the rough side facing outwards.
BONUS! Use the above method to create a custom shape lithophane! Load your image into Gimp For this process to work there shouldn't be any areas that are too white in the image or they will print very thin. If there are areas that are too bright, you can use reduce the brightness of the image a little clicking "Colors" and then "Brightness - Contrast". In this photo the white blouse isn't "pure" white, but in hindsight I should have reduced the brightness of the image a little bit. The result was still pretty good. Use the circle or rectangle tool to draw a shape around your subject. I'm going to create an oval shape. Now from the Gimp menu, pick "Select" and then "Invert". It will look the same but now you have selected the area on the outside of the oval shape. Click on the color swatch on the left side of Gimp and make sure the "R", "G", and "B" values are all set to "0". Now use the fill tool (bucket symbol) to fill the outside of the oval with pure black.
Now using the circle selection tool again, draw an oval a little larger than the first oval. Now once again pick "Select" and "Invert". Click on the color swatch on the left side of Gimp and make sure the "R", "G", and "B" values are all set to "255" (pure white). Now pick the fill tool and click outside of the oval to fill the outside area with white.
Now lets add a hanger loop. Pick the circle selection tool again and draw a circle at the tool the overlaps the black oval slightly. Change the color back to black again and fill the circle with black. Using the same process as above, draw a circle in the center of the black circle and fill it with pure white.
And finally, with the rectangle selection tool draw around the outside of the image. Then select "Image" and then "Crop to selection" so that the image is not larger than needed. Now save your image using "File" and "Export". Now load your image into Cura. This time we are going to set the "Base" to "0mm" Set your desired height. I used 4mm. Set the width or depth to whatever you like but don't make it too large because you may run out of memory :-)
Click ok to create the new model. Now it looks like there is a rectangular background on the model. However because it is so thin it won't actually print. Even if it does print, it will be easy to remove. Go ahead and use the "Save Model" command to export your lithophane. Here is the printed result!