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Course Library · Lesson 6 of 6
Digital · Guided lesson

Deliver pixel arithmetic and rendered evidence

About 26 minutes · 4 reading + 22 practice and checks
Time includes reading, practice, and questions. Extra videos or further study are optional.
See this course’s project requirements

A local original 4×4-to-64×64 pixel image tool with RGBA inspection, grayscale and threshold filters, preserved alpha and checked PNG export.

Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.

What to include

  • Produce a checked RGBA and coordinate-to-offset inspection table.
  • Demonstrate separate source/result buffers and a working original reset.
  • Calculate and verify equal-channel grayscale with alpha unchanged.
  • Produce a below/equal/above threshold matrix with preserved alpha.
  • Create and inspect the actual 64×64 PNG with intended crisp scaling and alpha behavior.
  • Deliver source, checked channel math, actual rendered/export evidence, and honest unavailable checks.

Review and revise

Use these criteria to check your work and choose what to improve.

  • The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
  • Normal, boundary and rejected cases are recorded with expected versus observed results.
  • The changed case has a correct explanation and does not rely on hidden state.
  • The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Open the full course project
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Before you begin

The idea in everyday life

Files pixels.html, pixel-filters.mjs and test-pixels.mjs supply an original 4×4 pattern: each row repeats red, green, blue, transparent white. Serve locally with python3 -m http.server 8765 --bind 127.0.0.1. Export scales the result to 64×64 PNG.

The idea

Pure array tests establish channel arithmetic; browser rendering and PNG inspection establish different artifact behavior. The final packet must preserve that distinction.

Follow along

Deliver pixel arithmetic and rendered evidence — original worked practice

Pure array tests establish channel arithmetic; browser rendering and PNG inspection establish different artifact behavior. The final packet must preserve that distinction.

Files pixels.html, pixel-filters.mjs and test-pixels.mjs supply an original 4×4 pattern: each row repeats red, green, blue, transparent white. Serve locally with python3 -m http.server 8765 --bind 127.0.0.1. Export scales the result to 64×64 PNG.

  1. 1. Step 1

    Run node test-pixels.mjs and retain the eight-check output.

    You should see: 8 pixel arithmetic checks passed.

    Pure array tests establish channel arithmetic; browser rendering and PNG inspection establish different artifact behavior. The final packet must preserve that distinction.

  2. 2. Step 2

    Compare browser Original, Grayscale, Threshold, and reset against the independent channel table.

    You should see: Actual rendered operations have their own observed results.

    Pure array tests establish channel arithmetic; browser rendering and PNG inspection establish different artifact behavior. The final packet must preserve that distinction.

  3. 3. Step 3

    Inspect the exported PNG and keep the original source files.

    You should see: The served/downloaded artifact evidence is retained.

    Pure array tests establish channel arithmetic; browser rendering and PNG inspection establish different artifact behavior. The final packet must preserve that distinction.

  4. 4. Step 4

    Deliver calculations, tests, output image, and unavailable browser/viewer notes.

    You should see: A pixel-processing project with exact verification scope.

    Pure array tests establish channel arithmetic; browser rendering and PNG inspection establish different artifact behavior. The final packet must preserve that distinction.

Now change one thing

Node arithmetic passed but no PNG was downloaded. How many delivered PNG files were inspected?

Your work

What to finish

Deliver source, checked channel math, actual rendered/export evidence, and honest unavailable checks.

Common mistake

Watch for this

Converting a pure array-test pass into a browser download or universal image-quality claim.

How can I tell I understand it?

Demonstrate the rule: Pure array tests establish channel arithmetic; browser rendering and PNG inspection establish different artifact behavior. The final packet must preserve that distinction. Use the supplied variant to distinguish a changed result from a broken implementation.

Try 3 questions

Quick knowledge check

Answer all 3 questions. Get at least 2 right and the lesson completes automatically.

Not yet passed

You’ll get an explanation for each answer. Signed in? Your results save to your account.

1What does the eight-check Node suite prove?
2What should happen if export returns a null Blob?
3Which final packet is complete within the declared scope?
0 of 3 answeredApply the lesson to a short question, then review the explanation.
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Finish this lesson

Pass the check. We’ll save the progress.

Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.

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Sources and further reading

Explore the references behind this lesson.

developer.mozilla.org — Pixel_manipulation_with_canvas
Source & access notes · checked 2026-10-01

Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.

Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.

Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.

developer.mozilla.org — putImageData
Source & access notes · checked 2026-10-01

Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.

Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.

Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.

developer.mozilla.org — toBlob
Source & access notes · checked 2026-10-01

Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.

Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.

Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.

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