8.B] Briefly explain arithmetic operations on images
Answer:
Arithmetic operations on images include addition, subtraction, multiplication, division, and blending. These operations are fundamental for various image-processing tasks.
Image Addition
Two images can be added directly as:
g(x,y) = f1(x,y) + f2(x,y)
The pixels of the input images f1(x,y) and f2(x,y) are added to obtain the resultant image g(x,y). When adding images, care should be taken to ensure that the sum does not exceed the allowed range (e.g., 0-255 for a grayscale image). If the sum exceeds this range, the pixel value is set to the maximum allowed value.
It is also possible to add a constant value to a single image, as follows:
g(x,y) = f1(x,y) + k
Where k is a constant. If k is positive, the overall brightness of the image increases.
Applications of Image Addition:
- Creating double exposure effects.
- Increasing the brightness of an image.
Image Subtraction
Image subtraction can be performed as:
g(x,y) = f1(x,y) - f2(x,y)
Where f1(x,y) and f2(x,y) are the input images. To avoid negative values, it is common to take the modulus of the difference:
g(x,y) = |f1(x,y) - f2(x,y)|
Subtraction can also be performed with a constant:
g(x,y) = |f1(x,y) - k|
Where k is a constant, reducing the overall brightness of the image.
Applications of Image Subtraction:
- Background elimination.
- Brightness reduction.
- Change detection.
Image Multiplication
Image multiplication is performed as:
g(x,y) = f1(x,y) * f2(x,y)
If the multiplied value exceeds the maximum allowed value, it is reset to the maximum. Scaling by a constant can also be performed:
g(x,y) = f(x,y) * k
Where k is a constant. If k > 1, the contrast increases; if k < 1, the contrast decreases.
Applications of Image Multiplication:
- Increasing contrast.
- Designing filter masks.
- Creating a mask to highlight areas of interest.
Image Division
Image division is performed as:
g(x,y) = f1(x,y) / f2(x,y)
Where f1(x,y) and f2(x,y) are the input images. This operation may result in floating-point numbers, so appropriate data types should be used. Division with a constant can also be performed:
g(x,y) = f(x,y) / k
Where k is a constant.
Applications of Image Division:
- Change detection.
- Separation of luminance and reflectance components.
- Contrast reduction.