Image resolution change is needed "for screens", that is, when posting your final artwork on social network websites, and "for print", that is, for printing your final artwork.
First of all, we are going to look at the resolution setting for screens.
From ① the Tool Selection window, select ② Canvas tool.
Select ① Resize.
Turn on ① Keep Aspect Ratio.
Resolution change for screens can be done by selecting ② Pixels.
For screens, you will be changing the pixel count (px), instead of dpi.
Change ③ the Width (px) from 1280 to 75. Once you are done, tap on ④ ✓ to finish.
Setting the pixel count to a significantly lower resolution worsens the image quality.
If you decrease the pixel count, you will get more maximum layer limit. Once you reach your maximum layer, try decreasing the pixel count. Also, decreasing the size of the canvas can help you work faster, and make the files take up less space on your device. Now, you can adjust the size of the screen with pixel count (px), and not with dpi.
Next, we will cover resolution settings for printing.
For artwork you would like to print, you can change the canvas size in mm and resolution (dpi). Set the dpi to minimum 300 for clean printed results. Dpi refers to dots per inch (25.4mm).
※Caution: when requesting a printing shop to print your artwork, make sure to be aware of your dpi and size. It is extremely difficult to change the dpi afterwards.
Turn on ① Keep Aspect Ratio. Changing resolution for artwork to be printed can be done by first selecting ② Print.
In print, select dpi. Adjust ③ the dpi from 350 to 10.
Once you are done setting the new value, tap on ④ ✓ to finish.
Decreasing the dpi as shown will worsen the image quality.
Next is an explanation of interpolation.
There are three "interpolation" methods: Nearest Neighbor (Pixel), Color Average (Pixel) and Bilinear.
Using each “interpolation”, here are the results when the image is enlarged or reduced in size.
In the following example, when enlarging an image, the left image above (with a width of 75) is enlarged to width of 1280 using "Keep Aspect Ratio". When reducing the image size, the right image above (with a width of 1280) is reduced to width of 75 using "Keep Aspect Ratio".
[ Bilinear ] … This setting is recommended for enlarging and reducing normal illustrations. When enlarging, it interpolates colors to prevent the pixels of the original (smaller) image from becoming visible (left image above). When reducing, it blends the colors of the original (larger) image to determine the colors of the new (smaller) image (right image above).
[ Color Average (Pixel) ] … When enlarging, it maintains a pixelated appearance (left image above). When reducing, it blends the colors of the original (larger) image to determine the colors of the new (smaller) image (right image above).
[ Nearest Neighbor (Pixel) ] … Recommended for enlarging and reducing pixel art. It maintains a pixelated appearance. Additionally, since it does not blend colors when reducing the image, no new colors that were not in the original image will appear.