Representing an image in binary - Answers
Q1. There are two different states a single can bit have: 1 and 0.
Q2. Image size information is held in the meta-data part of an image file.
Q3. Resolution is the number of pixels per square area.
Q4. Colour depth is the number of bits used to store the colour of each pixel.
Q5. The colour depth of a GIf FILE IS 8.
Q6. the colour depth of A JPEG FILE IS 16.
Q7. An image with a colour depth of 4 has up to 16 colours (2 to the power 4) in the picture?
Q8. Meta-data must hold information about the colour depth, image size, resolution and optionally, some information added by the author e.g. creation date, author, copyright info, GPS coordinates of photos etc.
Q9. A codec is a Maths formula applied to a bitmap file, which ultimately reduces its size for a very tiny loss, often unnoticeable, of detail.
Q10. A vector image doesn't store information about an image pixel by pixel. It stores formulas and information so that a picture can be redrawn from this data. This means that you can zoom in and out of a vector image without ever losing detail. If you keep zooming into a bitmap, you will eventually see the pixels.
Extension work a - b
Practical work. Students should get a good idea of the range of image file types and where and why each one might be selected by doing some Internet research. There are lots of good summaries. They should get experience using a vector drawing application such as SketchUp and a bitmap application, such as Paint, and saving / exporting to different codecs, and then be able to say what the advantages of one over the other might be. A useful exercise here would be to get students to do some scanning and look at the size of the resulting image, and then to export the bitmap to a range of other file types e.g. a JPEG, TIFF format and compare the file size. Students can also take pictures, add their own meta-data and send this to each other. They can investigate the meta-data held in an image file using applications like Irfanview.