Compression and File Size

This assignment tests your understanding of compression and file sizes.

If you missed the lesson, or would like to remind yourself, here are some helpful links:

Questions

The following questions are from GCSE Computing papers.

1. Explain the difference between lossy and lossless compression. (2 marks)
 
2. Give an example of a file that could be compressed and justify whether lossy or lossless compression would be best suited to this file. (3 marks)
 
3. The picture shown is stored as a black and white bitmap file.
Bitmap image
Calculate the size of the file in bytes assuming each pixel in the bitmap requires one bit of storage. Show your workings.
(3 marks)
   
4. A photographer downloads images from a website. The images are compressed.
Give one reason why images are compressed.
(1 mark)
   
5. A lossless, run length encoding (RLE) algorithm is used to compress the images.
This table shows some of the data for an image.
RLE source data
Apply RLE to the data and give the result.
(2 marks)
 
6. A lossy compression algorithm could be applied to the image data.
One feature of lossy compression is that it reduces the file size.
Give two other features of lossy compression.
(2 marks)
  a.
b.

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