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All modern graphic editors (for example, Blender, Gimp and others of that ilk) can use any raster image for Bump-mapping, using information about pixels' brightness. Let's take any texture as an example and see how it works.
Here is the texture "Stone Tile", that was taken from collection of the assistcg.com website. The texture is scaled down. The original size - 1024x1024 px.
Render from Blender-2.45 with the "Color" option activated
The same texture, but with the "Nor" option activated. This option allows to use usual raster image as Bump Map. The values for relief are taken from the values of pixels' brightness of our texture "Stone Tile".
Render from Blender-2.45 with the "Nor" option activated (in other editors "Bump")
Here is the texture "Stone Tile" with the "Color" and "Nor" ("Bump") options activated. The appearance of this texture becomes more relief and detailed.
Render from Blender-2.45 with the "Color" and "Nor" ("Bump") options activated
For more convenient work with texture parameters we recommend to put in one and the same texture in different texture channels, in such a way creating texture channels for Color Map and Nor (Bump) Map. Such an approach lets to turn off one texture channel while tweaking the other.
However, sometimes there's the necessity of adding some visual effects, for example noise, text or some image, that should look relief on your surface. For this we use either ready image with the "Nor" ("Bump") option activated or create special Bump map (texture). Such a map should be made up of two colors. A Bump map is basically a greyscale image that will tell, for each pixel of the rendered surface, if the local normal length should be scaled. If not, the pixel will be interpreted as laying on the "ground" level of the face (middle grey pixels (50 % grey) of the Bump map); if yes, it will be interpreted as laying above the ground (dark pixels of the Bump map) or under the ground (light pixels of the Bump map).
As an example let's take a 50 % grey background and add several black and white lines. This image will be our Bump map. The image was made in the Gimp 2.4.5, but one may use Photoshop.
To transform an image into Bump map the following actions should be executed:
1) The size of our Bump map should fit to the size of our basic image (Stone Tile).
2) The image's edges should be blurred for making soft transition (in this case a brush with soft edges was used).
3) Image's decolouration (if you use color raster image for making Bump map).
Let's add our created Bump Map to a free texture channel in Blender and activate the Nor option.
Render with associated textures Stone Tile and Bump Map
Happy Renders with assistcg.com !