What is colour depth?
Colour depth is the number of bits stored per pixel in a bitmap image
What is the impact of resolution and colour depth?
As the resolution and/or colour depth increases, the bigger the size of the file becomes on secondary storage
The higher the resolution, the more pixels are in the image, the more bits are stored
The higher the colour depth, the more bits per pixel are stored
Effects of compression
1 Less storage space required
#2 Less bandwidth required
#3 Shorter transmission time
Lossy compression
Lossy compression is when data is lost in order to reduce the size on secondary storage
Lossy compression is irreversible
Lossy & Lossless Text Files:
Lossy: ❌ Not suitable. Lossy methods remove data that cannot be recovered, which would change characters or corrupt the file.
Lossless: ✅ Used. Repeated patterns or characters are replaced with shorter representations using RLE. The original text can be restored exactly.
Lossy & Lossless Image Files:
Lossy: ✅ Used. Removes less important colour data and fine detail that the human eye is unlikely to notice. File size greatly reduced, but some image quality is permanently lost.
Lossless: ✅ Used. Identical pixels or repeating patterns are stored efficiently without losing data. File size smaller than original, but larger than lossy.
Lossy & Lossless Sound Files:
✅ Used. Removes frequencies outside human hearing range or quiet sounds masked by louder ones. Smaller files, but audio quality slightly reduced.
✅ Used when high quality is needed. Compresses by finding repeating patterns in the binary data without deleting any sound information. Original sound can be restored exactly
Lossless
Lossless compression is when data is encoded in order to reduce the size on secondary storage.
Lossless compression is reversible, the file can be returned to its original state.
What is RLE (Run-Length-Encoding)
Lossless compression method.
Reduces file size by replacing sequences of repeated data with a single data/value & count.
