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Questions and Answers
What is the formula for calculating dynamic range in terms of light?
Which dynamic range corresponds to normal imagery?
What issue arises from the incorrect use of dynamic range?
At what bit depth does 'false contouring' typically become apparent?
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For typical display purposes, what is the standard bit depth used per pixel?
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What is the primary difference between grayscale and color images?
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How many values typically represent a color in a color space?
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Which color space is recognized as the most common?
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What advantage does the HSV color space offer?
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What does an image histogram represent?
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What is the primary role of a charge-coupled device (CCD) sensor in digital image acquisition?
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Which operation is NOT a part of data preprocessing in image processing?
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The spatial resolution of an image primarily determines which aspect of image quality?
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In the context of image segmentation, which technique is primarily used for identifying moving objects in video?
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What does the variable 'I(x,y)' represent in digital image representation?
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Which of the following best describes the relationship between continuous images and discrete images?
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What characterizes the process of 'Brightness enhancement' in image processing?
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Which of these is NOT a feature of image characteristics?
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What is the primary purpose of compression in video recordings?
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Which of the following describes lossless compression?
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What is meant by 'temporal redundancy' in video compression?
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Which of the following codecs is considered a lossy compression method?
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In which scenario are keyframes used in video compression?
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What is the characteristic of images processed with lossless compression?
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How does the cumulative histogram function H(J) differ from the standard histogram?
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Which of the following refers to standard file formats that can use various codecs for video playback?
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Study Notes
Digital Image Acquisition
- The ubiquitous video camera is the source of imagery
- The Charge-coupled device (CCD) sensor is used to acquire images
- It measures brightness or intensity and color
- 3CCD is used for color images
- The CCD sensor has a rectangular array of detectors
Digital Image Representation
- Optical images can be expressed as I(x,y) where I(x,y) represents brightness at position (x,y)
- X and Y are spatial coordinates
- This can be digitally represented as a two-dimensional array
Image Characteristics
- Spatial resolution: A measure of image quality in terms of detail, determined by the CCD sensor
- Dynamic range: Measure of the range of brightness values a sensor can detect, usually expressed in bits (8 bits = 256 shades of gray)
- Gray-level quantization: Measure of the accuracy of the digitization process, represents how many levels of gray are used for a given dynamic range
- Color Space: Mathematical model that represents colors as a vector of numbers, providing features like invariance to color variation, shadows, reflections, and illumination changes. Common color spaces include RGB and HSV.
Image Histograms
- It visually shows the distribution of image pixels in terms of their gray levels
- It is a plot of Ni versus i, where Ni is the number of pixels with gray level i
- Cumulative Histogram: Shows the number of pixels with a specific value (number of pixels with value == J)
Image Compression
- Goal: Reduce the amount of information transmitted or stored by taking advantage of redundancy in images and videos
- Types of Compression: Lossless compression (perfectly reconstructs original data) and Lossy compression (approximates the original data)
- Common compression techniques: M-Jpeg, Mpeg, H.264, DIVX, WMV, Sorenson, 3GP.
- File formats (containers) like AVI and MOV can use these codecs.
- Common image compression techniques: JPEG, GIF, PNG
Video Processing
- Slow motion effect in video is achieved by increasing the frame rate.
- Compression techniques can be used to reduce the size of video files
- Temporal Redundancy is a significant source of information that can be used for compression
- Keyframes are frames without temporal compression (for example, change of scene)
- Framerates used in surveillance applications are typically low (1-2 frames per second) to save storage space and bandwidth.
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Description
Explore the fundamentals of digital image acquisition and representation in this quiz. Understand how CCD sensors work, image characteristics such as spatial resolution and dynamic range, and the representation of optical images as two-dimensional arrays. Test your knowledge of color spaces and gray-level quantization.
