What's Behind It All
What do you do if you have
a nice photo of a person, animal, or other image, but the background
is ugly or distracting, or you're really interested only in the main
subject? Well, the first thing you can do is remove the background.
(See Which Tool Should I Use to Cut Out an Irregular Image?)
But then what? Now you have an image just hanging in space.
This novice-level tutorial explains one technique you can use to create a textured background
for your image by using various GIMP filters and overlaid layers.
Step 1 — Create a Black Background
Open GIMP, set the Foreground
color to black, then choose File > New and create a new
image of an appropriate size. My image is 8.5 x 11 inches at 200
ppi. This will create a black layer named Background.
Step 2 — Create a Cloud Layer
To add some variability as
a base for the texture, the next step is to add a cloud layer.
Duplicate the background layer [1], then choose Filters >
Render > Clouds > Difference Clouds [2] and play with the
controls to create a cloud pattern that will look nice behind your
image. (Make sure the Preview box is ticked so you can see
what the filter will generate.) You can enter an integer in the
Random seed box, or use the up and down arrows, New Seed
button, or Randomize check box to change the seed. Ticking the
Turbulent box creates amorphous blobs as opposed to mist. The
Tilable option creates a rectangle of clouds that can be
copied and tiled with itself. Detail is a value from 1 (fuzzy)
through 15 (detailed) that adjusts the fuzziness of the clouds. X
size adjusts how stretched or compressed the clouds are in the X
dimension. Y size does the same in the Y dimension.
Once you have a cloud
pattern you're happy with, click OK, rename the new layer to clouds
[3], and turn the layer opacity down to somewhere between 30 and
50 percent [4].
Step 3 — Create a Spotlight Layer
The next step is to create
a highlight that will show around the cutout image that will be on
top of this textured background. This will set the image off as if
there's a spotlight shining on it. Create a new transparent layer [5]
at the top of the Layers list. Using the Ellipse Select tool
[6], drag out a fair-sized oval and use the Bucket Fill tool
[7] to fill the oval with white.
Then choose Layer >
Transform > Arbitrary Rotation [8] and rotate the oval in a
direction consistent with the lighting of your image.
This will create a
Floating Selection (Transformation) layer [9]. Right-click on
it and choose Anchor Layer [10].
Choose Filters >
Blur > Gaussian Blur [11] and enter a very high number [12]. I
entered 1000.
Rename the layer to
spotlight [13] and lower the opacity to somewhere between 50
and 70 percent [14].
Step 4 — Create a Texture Layer
It's time to to add some
noise or graininess. Create a new layer at the top of the Layers list
and fill it with white.
The fun part now is
experimenting with the Artistic filters. I chose Filters >
Artistic > GIMPressionist [15]. The Preset <Factory
defaults> will generate some directional noise. The angle can
be adjusted in the Orientation tab with the Angle span
setting. Pressing the Update button will show a preview of
what the filter will generate.
To try another Preset,
click on a name on the Presets tab [16], then click the
Apply button [17], then the Update button [18]. When
you're happy with the preview, click OK [19] to run the
filter, which will change the white layer. If you don't like the
result, use CTRL+Z, then choose other settings or another
filter. If you just want some random noise, choose one of the noise
filters from the Filters > Noise menu.
Once you've settled on a
filter effect that you like, rename the layer to filter [20]
and adjust the layer opacity [21] so that it adds a nice level of
texturing to the background. Here's the result of my choice of
Crosshatch.
Step 5 — Save a Reference File
At this point you should
have a file containing four layers: a black background layer, a
clouds layer, a spotlight layer, and a filter layer. Save this file
as a reference. If you should ever need to create another
background, you can copy this file and change any or all of the
clouds, spotlight, and filter layers independently.
Step 6 — Colorize the Textured Background
The final step is to add
some color to the textured background (assuming you want something
other than a grayscale version). First, you need to combine all the
layers into one layer that can be colorized. The easiest way to do
this is to right-click in the Layers list and choose New from
Visible [22]. This will create a layer named Visible [23].
Next, add your cutout
image as the top layer by dragging the image file from the file
explorer onto the textured image. Then, with the Visible layer
active, choose Colors > Colorize [24] and slide the
Hue slider [25] back and forth until you find a color that
goes with your image. Press OK [26] to save the color.
[NOTE – 02 Oct 2013: A better way to color the background is to add a new layer of a solid color above all the texture layers and set its layer Mode to Color. Then use Colors > Hue-Saturation to adjust the color as necessary. This method is much more flexible.]
When you're satisfied with the look of your complete image, export it with File > Export to a raster (.jpg, .png, etc.) file.
When you're satisfied with the look of your complete image, export it with File > Export to a raster (.jpg, .png, etc.) file.
UPDATE – 13 March 2014
I have recently switched to using the fog filter (Filters > Render > Clouds > Fog) most of the time. I set the Fog color to a light to medium gray and the Turbulence to somewhere between 0.8 and 1.2. Every time the filter executes it generates different output. Sometimes I have to run it only once to get a look I like. Other times I run it several times until I see something I like. I place the fog layer over a black layer and adjust the opacity of the fog layer to something that looks good. Then I create a complementary color layer over the fog layer and change the layer mode to Color. Occasionally I'll import a photo of a texture (like stucco, for example), desaturate it, and place it between the fog layer and the color layer with an opacity that looks good. This technique of creating a background tends to look really nice behind photos of animals. For an example, see my processed photo called Bird on a Catwalk.
Related GIMP Tutorials
How to Create a Textured Background Using Color Functions and Bump Maps
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