Which processing step is used to adjust brightness and contrast of a digital image?

Which processing step is used to adjust brightness and contrast of a digital image?

• A. LUT Adjustments
• B. Histogram Analysis
• C. Rescaling
• D. Digitization

Answer: (A)

Brightness and contrast are controlled by modifying the look-up table that maps each input pixel value to a displayable gray level. The LUT defines, for every possible input value, what output value to show. By changing this mapping, you shift the overall brightness (adjusting the baseline output values) and alter contrast (changing how rapidly output values change with input values). This LUT-based approach is what window leveling and window width mechanisms rely on in digital radiography, making it the direct and effective method for adjusting how an image appears on the monitor. Histogram analysis, while useful for informing how to set brightness and contrast by describing the distribution of pixel values, does not itself change the image. Rescaling could change the range of displayed values, but the standard, targeted means of adjusting brightness and contrast in DR is through LUT adjustments. Digitization is the process of converting analog signals to digital form and does not adjust brightness or contrast.

Brightness and contrast are controlled by modifying the look-up table that maps each input pixel value to a displayable gray level. The LUT defines, for every possible input value, what output value to show. By changing this mapping, you shift the overall brightness (adjusting the baseline output values) and alter contrast (changing how rapidly output values change with input values). This LUT-based approach is what window leveling and window width mechanisms rely on in digital radiography, making it the direct and effective method for adjusting how an image appears on the monitor.

Histogram analysis, while useful for informing how to set brightness and contrast by describing the distribution of pixel values, does not itself change the image. Rescaling could change the range of displayed values, but the standard, targeted means of adjusting brightness and contrast in DR is through LUT adjustments. Digitization is the process of converting analog signals to digital form and does not adjust brightness or contrast.