Lecture Notes: Representing Images in Binary

Introduction to Bitmap Images

• Bitmap images are stored as 2D arrays of individual pixels.
• Pixels are the smallest distinguishable feature of an image.
• Images and monitors are divided into rows and columns of pixels.
• The size of an image or monitor is expressed in pixels (width x height).
• Resolution refers to the detail or density of pixels in an image.

Resolution

• Resolution can be expressed in various ways:
  • Width x Height in pixels
  • Pixels Per Inch (PPI) or Dots Per Inch (DPI)
• Higher resolution means more details in an image.

Image Capture Process

• A grid is overlaid on an image to determine pixel color.
• Each pixel is assigned a binary value based on its color.
  • For black and white images, pixels can be either 0 or 1.
  • For color images, multiple bits are used to represent a pixel.

Color Depth

• Color depth (or bit depth) is the number of bits per pixel.
• Black and white images use 1 bit per pixel.
• Color images require more bits:
  • 3 bits can represent 8 colors (2^3=8).
  • Color depths of 4, 8, and 24 bits can represent 16, 256, and ~17 million colors, respectively.
• Higher color depth increases image quality but also file size.

Calculating File Size

• File size can be determined by:

  File Size (in bits) = Width in pixels x Height in pixels x Color depth in bits

• Convert bits to bytes for practical sizes:

  • 8 bits = 1 byte
  • 1,024 bytes = 1 kilobyte (KB)
  • 1,024 kilobytes = 1 megabyte (MB)

Metadata

• Metadata is data about data, crucial for displaying images properly.
• Important metadata for images includes:
  • File name and format
  • Color depth and resolution
  • Camera details (e.g., aperture, make, model) can be included but are not necessary.
• Metadata helps in processing and displaying the image.

Conclusion

• Understanding the relationship between resolution, color depth, and file size helps in managing image quality and storage efficiency.
• Metadata plays a key role in how images are stored and displayed.