Image Processing: Sampling
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Questions and Answers

What is the primary purpose of image sampling in digital imaging?

  • To display images in a higher resolution
  • To compress image data for storage
  • To reduce the pixel density of an image
  • To represent the measurements of light intensity or color numerically (correct)

    • What happens when an image is sampled with a lower sampling frequency in both spatial dimensions?

  • The pixel density decreases (correct)
  • The image remains unchanged
  • The image resolution increases
  • The image becomes distorted

    • What is the result of interpolating a subsampled image using a zero-order interpolation method?

  • Each pixel is duplicated to fill the original size (correct)
  • A blurry image is produced
  • A checkerboard pattern is displayed
  • The image is rotated by 90 degrees

    • How are pixels typically indexed in a digital image?

    <p>Using Cartesian coordinates (x, y)</p> Signup and view all the answers

    What is the outcome of quantizing the value of the image function f(x, y)?

    <p>The image function is digitized</p> Signup and view all the answers

    What is the term for the small square area of the image that corresponds to each sample?

    <p>Pixel</p> Signup and view all the answers

    What is the total number of gray levels in the subsampled images?

    <p>256</p> Signup and view all the answers

    What is the effect of reducing the number of samples in the subsampled images?

    <p>Checkerboard pattern appearance</p> Signup and view all the answers

    What is the process of deleting rows and columns from the original image to obtain smaller images?

    <p>Subsampling</p> Signup and view all the answers

    What is the resolution of the smallest subsampled image?

    <p>32×32 pixels</p> Signup and view all the answers

    What is the purpose of bringing the subsampled images up to size 1024×1024 by row and column pixel replication?

    <p>To observe the effects of subsampling</p> Signup and view all the answers

    What is the observed effect in the 256×256 image in Figure 2(c)?

    <p>Slight fine checkerboard pattern</p> Signup and view all the answers

    What is the primary purpose of quantization in digital image processing?

    <p>To represent the brightness of each pixel by an integer value</p> Signup and view all the answers

    What is the effect of reducing the number of quantization levels in an image?

    <p>It decreases the accuracy of the image representation</p> Signup and view all the answers

    What is the typical case of a monochrome image?

    <p>An image with 256 reconstruction levels</p> Signup and view all the answers

    What is the visual effect of reducing the number of reconstruction levels in an image?

    <p>It results in the appearance of false contours</p> Signup and view all the answers

    What is the purpose of binary coding in image processing?

    <p>To represent the magnitude of each pixel by an integer value</p> Signup and view all the answers

    What is the relationship between the number of quantization levels and the accuracy of the image representation?

    <p>The more levels, the better the approximation</p> Signup and view all the answers

    Study Notes

    Image Sampling

    • Image sampling is a process of creating a digital image from data acquired by a camera or other imaging instrument
    • It requires a two-dimensional pattern to represent measurements (light intensity or color) numerically
    • Examples: Lena image sampled with two different sampling structures, resulting in different resolutions (256x256 and 64x64 pixels)

    Sampling Frequency

    • Sampling frequency affects the resolution of the image
    • Lower sampling frequency results in a lower resolution image (e.g., 64x64 pixels)
    • Higher sampling frequency results in a higher resolution image (e.g., 256x256 pixels)

    Pixels

    • A digital image is a two-dimensional array of pixels
    • Each pixel corresponds to a small square area of the image
    • Pixels are indexed by x and y coordinates, with x and y taking integer values

    Quantization

    • Quantization is the process of digitizing the value of the image function f(x, y)
    • It involves replacing a continuously varying f(x, y) with a discrete set of quantization levels
    • The accuracy of quantization depends on the number of quantization levels used

    Effects of Reducing Number of Samples

    • Reducing the number of samples can result in a loss of detail and a checkerboard pattern effect
    • Examples: subsampling an image from 1024x1024 to 512x512, 256x256, and 32x32 pixels
    • The effects of reducing the number of samples become more pronounced as the image size decreases

    Quantization of an Image

    • Quantization of an image involves representing the brightness of each pixel by an integer value
    • The number of quantization levels determines the accuracy of the representation
    • Examples: quantization with 8 bits per pixel (256 reconstruction levels), 4 bits per pixel (16 reconstruction levels), and 2 bits per pixel (4 reconstruction levels)

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    Description

    Learn about image sampling, a crucial process in digital image creation, where a 2D pattern represents measurements of light intensity or color. Explore examples of sampling structures and their effects on image quality.

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