Question

Using the examples presented for displaying an image in Matlab together with those for accessing pixel locations, investigate adding and subtracting a scalar value from an individual location, i.e. I(i,j)=I(i,j)+25 or I(i,j)=I(i,j)−25. Start by using the grey-scale 'cell.tif example image and pixel location (100,20). What is the effect on the greyscale colour of adding and subtracting? Expand your technique to RGB colour images by adding and subtracting to all three of the colour channels in a suitable example image. Also try just adding to one of the individual colour channels whilst leaving the others unchanged. What is the effect on the pixel colour of each of these operations?

Answer 1

When adding a scalar value to a pixel in an image, the grayscale color becomes brighter, while subtracting a scalar value makes it darker. In RGB color images, adding or subtracting scalar values affects the overall color. Adding to one color channel only results in a color shift.

Step-by-step explanation:

When adding a scalar value to an individual pixel location in an image, such as I(i, j) = I(i, j) + 25, the effect is to increase the grayscale color of that specific pixel. Adding a scalar value will make the pixel appear brighter and lighter. Conversely, when subtracting a scalar value, such as I(i, j) = I(i, j) - 25, the effect is to decrease the grayscale color of the pixel, making it appear darker.

When working with RGB color images, adding and subtracting scalar values to all three of the color channels will result in a change in overall color. For example, adding a scalar value to all three channels will make the image appear brighter and lighter in color, while subtracting a scalar value will make it appear darker.

If you only add a scalar value to one of the individual color channels while leaving the others unchanged, the effect is to introduce a color shift to the image. For example, adding a scalar value only to the red channel will make the image appear more red, while the other colors remain the same.