In part1 and part2 of GIMP series, we learned about the basic editing tools and selection tools. Now taking image manipulation to next level, in this article we will cover some advanced features of this editor.
Gimp Image Editor – Coloring tools
Coloring is an integral part of image editing.
For coloring you can choose a foreground colour and fill it in the selection with the option “Fill with FG color”. Similarly, you can select background color, fill it with option “Fill with BG color” and then also fill the selection with different patterns.
1. Color Balance
Color Balance tool changes the color balance of the selection or complete layer. You can select from the ‘Range to Adjust’ in which shadows are the darkest pixels, midtones are the medium and highlights are the brightest ones. Then you can select from ‘Adjust color levels‘ in which zero position on the slider corresponds to the current value level of the pixels in the original image. Here, you can change the pixel color towards either of the two colors in all three options. You can very well observe the change in pixel colors from the screen-shot below.
2. Hue Saturation
Hue Saturation tool will enable you to adjust hue, saturation and lightness on the range of color that you select for the selection. You can can select a primary color to adjust, for example I selected red color and then adjust the hue, lightness and saturation on that color by moving slider from zero(th) position.
Colorize tool turns the selection into a greyscale image or gives sepia effect to your image. Then you can adjust the level of hue, saturation and luminosity over it using the sliders.
The Brightness-Contrast tool adjusts the levels of brightness and contrast for the active layer or the selection.
Threshold option enables you to transform the selection or the layer into black and white image. You can select the range of threshold by sliding black or white triangle.
Levels tool majorly works on shadows and highlights. This option allows you to change the intensity of colors on a selection in different channels. You can make image lighter or darker by adjusting levels. You can select a particular color like I selected green which works on a particular color channel and you can see that in the image. Similarly, blue and red works on particular color channels and will bring different results on the image. Moving further, input and output levels can be modified using slider option. One of the channel options is alpha which works only on semi-transparent layers. If your image doesn’t have alpha channel, this option remains disabled.
Curve tool basically works on the tonal range of the image. It transforms the color, contrast, brightness and transparency of the selection or active layer. There are two types of curves, one is smooth and other is free hand. First of all, you select a channel where in you have different options. Under channel, in value, curve represents the brightness of pixel; in “RGB”, curve represents the quantity of color; in “alpha”, curve represents opacity of the pixel. Reset channel will reset the default values by deleting the changes made to the selection.
Posterization reduces the number of colors. You can move the slider to reduce the number of colors in the image.
Desaturation enables you to convert all the colors of selection or active layer to the corresponding shades of gray color.
Under this option, you can invert all the pixel colors and brightness values of the selection as if the image is converted into a negative where bright areas become dark and dark areas become bright.
11. Value Invert
This option inverts the luminosity of the selection or active layer without affecting the hue and saturation.
Auto command has six options which are :
‘Equalize‘ that automatically adjusts the brightness of the colors over the selection.
‘White Balance‘ that automatically adjusts the colors of the selection by stretching RGB channels separately.
‘Color Enhance‘ automatically increases the saturation of the colors in the active layer without affecting brightness or hue.
‘Normalize‘ which automatically stretches the brightness values to cover the full range.
‘Stretch Contrast‘ automatically stretches the contrast to the maximum possible range.
‘Stretch HSV’ also stretches the contrast but in HSV color space rather than working in RGB color space.
Components consist of a Channel Mixer and Decompose. Channel mixer alters the colors by mixing RGB channels. Decompose command decomposes an image into separate color space components, you can select the color model like I selected HSV i.e. Hue, Saturation and Value.
Map command further has eight options which are :
- Re-arrange color map,
- Set color map,
- Alien map,
- Color exchange,
- Gradient map,
- Pellet map,
- Rotate colors,
- Sample colorize.
Under this command, you can re-arrange color map, set a new color map, alter colors in various ways, swap colors, re-color the image using active gradient, re-color the image using the colors from the active pallet, replace the range of colors with one another and colorize the image using sample image as guide respectively.
Re-arrange color map:
Info section consists of a histogram, border average, color cube analysis and smooth pallet which gives you information about the statistical distribution of color values in the selection, set foreground to average color of the image border, analyse the set of colors in the image and derive a smooth color pallet from the image respectively.
16. Color to Alpha
This command converts a specified color in the selection to transparency. For example, I selected blue color and it got transparent showing the layer underneath.
This command replaces all colors with shades of a specified color.
18. Filter pack
This tool interactively modifies the colors in the image.
19. Maximum RGB
This command reduces image to pure red, green or blue.
This command enhances the contrast using the retinex method.