Inverse Log Transformation in Image Processing: Gamma Correction Quiz and Flashcards

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Questions and Answers

What is the purpose of a log transformation in image processing?

To expand values of dark pixels while compressing higher level values.

Explain the effect of using fractional values of gamma in power-law transformations.

Fractional values of gamma map a narrow range of dark input values into a wider range of output values.

What happens when gamma value in power-law transformations is greater than 1?

Curves generated with gamma > 1 have the opposite effect of curves with gamma < 1.

When c = 1 and gamma = 1 in power-law transformations, what transformation is applied?

Identity transformation is applied. Signup and view all the answers

How does gamma correction help in image processing for cathode ray tube (CRT) devices?

Gamma correction helps adjust the intensity-to-voltage response of CRT devices. Signup and view all the answers

What is the significance of using a thresholding function in image processing?

Thresholding function helps separate objects from the background based on intensity levels. Signup and view all the answers

What is the purpose of using the negative transformation on an image?

Enhancing white or grey detail embedded in dark regions of an image Signup and view all the answers

Describe the form of the intensity transformation function for contrast stretching.

s = T(r) where s and r are variables denoting intensity at any point, T(r) brightens intensity levels above k and darkens levels below k Signup and view all the answers

What type of image does a thresholding function produce?

Binary image Signup and view all the answers

Explain the purpose of a log transformation in image processing.

Maps a narrow range of low intensity values into a wider range of output levels Signup and view all the answers

What does the log transformation expression s = c log(1+r) do to the input intensity values?

Maps low input intensity values into a wider range of output levels Signup and view all the answers

How does the power-law (gamma) transformation function differ from other intensity transformations?

Uses a power-law expression to adjust image contrast Signup and view all the answers

What is the general form of a Log Transformation function?

s = c * log(1 + r) Signup and view all the answers

What is the goal of Intensity level slicing in Piecewise-Linear Transformation Functions?

To highlight a specific range of intensities Signup and view all the answers

What is the purpose of Contrast Stretching function?

To expand the range of intensity levels to span the full intensity range of the output device Signup and view all the answers

What is the formula for a Power-Law (Gamma) Transformation?

s = c * r^gamma Signup and view all the answers

What is the formula to obtain the negative of an image with intensity levels in [0, L-1]?

s = (L-1) - r Signup and view all the answers

What problem does a Power-Law (Gamma) Transformation with gamma > 1 aim to solve?

To compress intensity levels, especially when the image has a 'washed-out' appearance Signup and view all the answers

Study Notes

Log Transformation

Purpose: to compress the dynamic range of an image, reducing the effect of extreme brightness values
Expression: s = c log(1+r), which compresses high intensity values and expands low intensity values

Power-Law (Gamma) Transformation

Formula: s = c*r^γ, where γ is the gamma value
Effect of fractional values of γ: produces non-linear transformations, useful for correcting non-linear responses of devices
When γ > 1: expands the darker regions of the image, compressing the brighter regions
When c = 1 and γ = 1: applies an identity transformation, leaving the image unchanged
Purpose: to compensate for non-linear responses of devices, such as CRT devices, to improve image quality

Thresholding

Purpose: to segment an image by separating objects from the background
Produces a binary image, where pixels are classified as either object or background
Significance: useful in object recognition, feature extraction, and image analysis

Negative Transformation

Purpose: to invert the intensity values of an image, making dark regions bright and vice versa
Formula: s = L - 1 - r, where L is the maximum intensity value
Effect: useful for enhancing details in dark regions of an image

Contrast Stretching

Purpose: to enhance the contrast of an image, making it more visually appealing
Intensity transformation function: linear scaling of intensity values to a desired range
Effect: improves the visibility of details in an image

Piecewise-Linear Transformation Functions

Goal of Intensity level slicing: to separate objects from the background by selecting specific intensity ranges
Purpose: to apply different transformations to different intensity ranges in an image

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Power-law and Inverse Log Transformations in Image Processing