9 Questions
What best describes a raster image?
It consists of elements like pixels.
Which of the following is a typical format for vector images?
EPS
What do we call the projection of both raster and vector images into a grid of colored elements for display?
Rasterization
What is the spatial resolution of an image mainly dependent on?
Number of pixels per unit length
Which factor affects an image's ability to represent fine details?
Resolution
Why is it recommended to avoid digital zoom for capturing a large image with good detail representation?
Digital zoom introduces probable pixels between real ones.
What does DPI stand for in relation to digital images?
Dots per Inch
Which file format is NOT typically associated with raster images?
.SVG
What is the primary difference between a raster image and a vector image?
Raster images show smooth structure when zoomed while vector images show colored elements.
Study Notes
Image Size and Resolution
- Image size refers to the number of pixels in a digital image, measured in width x height.
- Resolution is the number of pixels per inch (PPI) or dots per inch (DPI), with higher resolution yielding better quality.
Image Size Calculation
- Formula: Total image size = header size + data size
- Data size = width * height * no.of bits/pixel
- Example: 6x4 inch image at 150 PPI, header file size = 10 bytes, total image size = 67510 bytes = 65.92 Kbyte
Gray Scale Image Size Calculation
- Formula: Data size = width * height * 8
- Example: 200x200 pixels, header file size = 80 bytes, total image size = 40080 bytes = 39.14 Kbyte
Color Image Size Calculation
- Formula: Data size = width * height * 3 (for 24-bit color image)
- Example: 400x400 pixels, header file size = 100 bytes, total image size = ?
24-bit Color Images
- Each pixel is represented by three bytes, representing RGB
- Supports 256 x 256 x 256 possible combined colors, or a total of 16,777,216 possible colors
- Stored as 32-bit images, with an extra byte of data for Alpha value representing special effect information (e.g., transparency)
Image Presentation
- Frame buffer: hardware used to store bitmap, typically on a graphics card
- If not enough video card memory, data is shifted around in RAM for display
Digital Image Definition
- Raster image or bitmap: composed of elements that appear when zoomed
- Vector image: does not consist of elements, can be zoomed smoothly
Vector vs. Raster Images
- Raster image: used for photorealistic images, typical formats include JPEG, TIFF, GIF, PNG, etc.
- Vector image: used for simple graphics and drawings, typical formats include EPS, AI, CDR, WMF, DXF, etc.
How We See Digital Images
- Raster and vector images are projected into a raster of colored elements (pixels) when displayed or printed
- Resolution or spatial resolution is the number of pixels per unit of length, usually given as dots per inch (dpi)
Test your knowledge on calculating image sizes and resolutions. This quiz covers concepts such as the number of pixels in a digital image, pixels per inch (PPI), dots per inch (DPI), and how to calculate binary image sizes based on resolution and dimensions.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
