Count Pixels in a Grid

Supplied materials

• Paper and pencil; answers may also be spoken or typed.
• All cases, labels, numbers and rules are supplied on this page. No real account, private information or purchase is needed.

Learn the idea

A digital raster picture is represented by a grid of pixels. Each position has a recorded value such as a color. Counting positions uses rows times columns, not rows plus columns. This paper model assigns one value per pixel and ignores compression and file overhead.

Multiply the number of rows by the number of columns to count pixel positions. The count of positions is not automatically the file size in bytes.

Use this supplied case: A paper pixel image has 2 rows and 3 columns. How many pixel positions need values? Use the details in this example. Say which detail helped you choose. This pretend example does not tell us how every real system works.

1. Follow the worked example one step at a time. Say or draw what happens.
2. Multiply the number of rows by the number of columns to count pixel positions.
3. Say which detail makes the example answer fit. Pick another answer and say why it does not fit.
4. Try the question and practice questions. Read the rule again if your answer does not match the explanation.

Check your reasoning

Your answer is temporary and is not saved to an account. Download your current answer before leaving or reloading. Written work on paper or in another app stays in your own file.

Take it further

New raster grid has 3 rows and 5 columns. Expected:15 pixel positions. This is a position count, not automatically a byte-size claim.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback. It does not include choices from the separate More practice section. Download that section separately.