Paint.net (continued)

Improving an image

Let's start by adjusting the colour balance. There is a very practical Paint.net plug-in, named Whitepoint, available here. To install it, unzip the archive and place the Whitepoint.dll file into C:\Program Files\Paint.NET\Effects.
(Note: "Program Files" may be named "Programs" in Vista and Windows 7+).

If you took the precaution, as I advised you, to have in the photo a neutral zone (the background, a white reflector or a gray ground), just take this supposed neutral colour with the colour pipette, then launch Adjustments / Whitepoint. You can then verify that the reference point has its R, G and B components almost equal.

Adjustments, Levels

Then, you can try to improve the image (levels, brightness, contrast, framing). The Levels and Curves functions in the Adjustments menu are very useful. The first is more difficult to apprehend than the second, but gives often faster results. Avoid Brightness and Contrast that may remove pixels (either lighter or darker), thus reducing the richness of the image.

The curve to the right allows to lighten the shadows, to see a little more details for example on the tires of a car.

Adjustments, Curve

Original image

Original image: the background is greyish, but very neutral.
Lada Niva Brekina réf. 27201

Creating a mask

In the Layers window, let’s duplicate the image. On this copy, apply the Effects / Color / Threshold function which transforms any pixel into either pure white or pure black. The extreme contrast in short… By playing with the slider, you can get a black silhouette on a white background.

Note: Threshold is a plug-in. There are several. The one that I propose to you is at this address. After extracting the files from the Zip archive, place the EdHarvey. Effects.dll file into C:\Program Files\Paint.NET\Effects and EdHarvey.Effects.pdb into C:\Program Files\ Paint.NET\ FileTypes
(attention : "Program Files" may be named "Programs" in Vista and Windows 7+).

Duplicate layer

Sometimes, the model itself has very clear parts that are likely to be eliminated. Before applying Threshold, let's draw the inner contour of these zones with a black line 10 pixels thick (approximately), after having disabled the antialiasing (antialiasing means that, seen at 100%, a line must present frank, not blurred “stair steps”). The line has four handles that allow it to be moved or deformed, for example to follow a curve. If it is missed, delete it by Esc. You may also use Undo (Ctrl + Z) to go back. When the line suits your needs, validate by Enter.

Antialiasing

On the other hand, if there are any black spots in the future background, don’t worry: they will be eliminated by the process, provided they don't touch the main silhouette.

Finally, we get what was already called a mask in the times of the analog photo laboratory. Let’s verify by magnifying the image that white pixels (due to reflections on chromes for example) do not remain encrusted in the black silhouette. In fact, the whole mask must be well filled.

Mask

The mask, including the ground

Creating the “sky” selection

Let’s select the mask with the Magic Wand, then reverse the selection (Edit / Invert Selection menu, or more simply Ctrl + I). So the future “sky” is now selected.

Sky

The selection of the “sky”, ready to receive the gradient