Computer Graphics

Basics: Colors

We will now look into working with colors in an image and we'll also learn to combine layers in a creative way. The goal of this tutorial is to take a normal photo and give it a movie-like look.

Download and open this photo (or find some other photo on the Internet):

1. Start

We start by opening the photo. There will be only one layer (containing the photo) and we rename this layer to Original.

Right click on the Original layer and duplicate it.

Rename the duplicate layer to Movie.

You can hide the Original layer (click on the eye icon next to it). We will not be working with it. It only serves as a backup or to compare your result to the original photo.

2. Tweak the colors

Select the Movie layer. Now go to the main menu Colors > Hue-Saturation. A dialog window will open where you can play with the brightness of the image, its saturation or its color tone. We will only turn down the Saturation to -45. Like this:

The image lost some of its colorful appearance and might look a bit dull. Let's add some drama to it...

Go to main menu Colors > Curves. This will open another dialog. This allows us to change how different brightness levels of the image will apear. By default, the curve is a straight line. We want to make it lower in the left part and a bit higher in the right part. Just grab the straight line and drag it to make it into a slightly 's'-shaped curve:

3. Depth of field

Depth of field is a camera effect where the focus is on a certain object or a certain distance which is displayed as sharp. The rest of the screen gets gradually blurrier as we move outside of the focus area. Our photo is sharp in all areas and therefore we will create this effect now.

Duplicate the movie layer and rename the new layer to Blur. We now have three layers: Original, Movie and Blur:

Select the Blur layer. Go to main menu Filters > Blur > Gaussian blur. Set the blur radius to 5 and blur the image:

Of course, not whole image should be blurry. We will mask some parts of the Blur layer to reveal the sharp Movie layer below.

Create a new mask for the Blur layer. It should be completely white by default.

Now select the Blend tool for creating gradients and set the gradient options to go from FG to BG (this is the default option) and change its shape to Bi-linear:

This type of gradient creates a linear gradient which stretches symmetrically to both sides. Make sure you have the layer mask of the Blur layer active. Click in the middle of the image a drag the gradient down a bit like this:

This should be your intermediate result:

The central part of the image is sharp. The areas closer to the camera and further from the camera are blurry. That is the depth of field effect.

4. Wide-screen

Aspect ratio of an image is its width:height ratio. Movies usually have a high aspect ratio (e.g. 16:9 or even 21:9) while photos often have a lower aspect ratio (4:3). To create the widescreen effect, we will add two black horizontal bars to the image. One to the top and one to the bottom. This is called letterboxing.

Create a new layer and call it Letterbox. This layer should be the top layer. Even after we create some new layers later on, make sure there are place below the Letterbox layer in the layers panel.

Now take the Rectangular selection tool (R) and draw a rectangle in the upper part of the image:

Make sure you have the Letterbox layer active and fill the selection with black color using the Bucket fill tool (Shift+B). Repeat the same in the bottom of the image. This should be your picture now:

5. Vignette

Another property of a movie image is the vignette effect which makes the border areas of the picture darker than the center parts.

To simulate this effect, we create a new layer and call it Vignette.

Take the Paintbrush tool (P), pick a large brush with soft border and increase the sice of the brush to 100-150px. Draw black borders inside the Vignette layer using the brush:

This is of course not the final result. We will now smooth out the vignette by applying the gaussian blur. Go to main menu Filters > Blur > Gaussian blur and set the blur radius to 150:

Decrease the opacity of the Vignette layer to 75. Notice how the Vignette layer is below the Letterbox layer in layers panel.

It's starting to look like a movie after all:

6. Adding noise

Traditional movies filmed on analog often contain a specific noise. Let's add some noise to our photo as well.

Once again, create a new layer. This time name it Noise. Move it under the Letterbox layer in layers panel. Use the Bucket fill tool and fill the layer with white color. This is your picture now:

Go to Filters > Noise > HSV noise. A dialog will open and we set Holdness = 2, Hue = 0, Saturation = 0, Value = 50:

This settings will create a noise in the Noise layer and restricting the noise to Value only (Hue and Saturation noise is 0) will only create dots with different brightness. Not with different color.

The Noise layer is a layer containing black-and-white noise now. Each layer has a certain way (or mode) in which it is combined with the layers below it. This is set in the Layers panel, above the Opacity:

By default, each layer is combined in 'Normal' mode. Click on the Noise level. Then click on is mode and change it to Multiply:

The Multiply mode takes each pixel of the Noise layer and multiplies the pixels in the below layers by it. This means that white pixels in Noise layer don't do anything, black pixels result in black color, gray pixels appear darker than the pixels in layers below. This is the image multiplied by the noise:

7. Color filter

The last effect we'll add is a color filter. This is often used by movie directors to create a certain 'mood' in the movie. Let's create yet another layer, name it Mood.

Fill the Mood layer with a cyan-greenish color and move it below the Noise layer. Set its opacity to 25. Set its mode to Overlay.

The Overlay mode combines the layer with the layers below in a similar way as if a colored glass was placed over the image. That's why it simulates the movie camera's color filter so well.

This is your result now:

You can try to fill Mood layer with a different color to create different moods.