Brightness Modification

We can't read a book or see something clearly in a room with low light source. In real life, we can improve brightness by exposing the object with strong light source. In image processing, it's equivalent to white color (analogous to light source) addition. This is done by simply adding a constant to each color element. When the constant is positive then the image become brighter and when the constant is negative then the image will be darker.

Figure 1. Brightness Manipulation Function Plot

The GST function for brightness manipulation ca be plotted as shown in figure 1. Remember that the addition with the constant is limited to 0-255 (8bit monochrome or 24bit true color format). The effect on the image's histogram is shown in figure 2.

Figure 2. Brightness Manipulation Effect on Image Histogram

For true color image, the modification for each color elements can be different. We can add more blue and reduce the red element to make different color source addition (equivalent to color light source exposure in real life).