Apply a threshold with a stated boundary
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.
Want more background?
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.
Thresholding maps the computed mean to black or white under a precise cutoff. This rule uses mean≥120 for white; below 120 becomes black.
Apply a threshold with a stated boundary — original worked practice
Thresholding maps the computed mean to black or white under a precise cutoff. This rule uses mean≥120 for white; below 120 becomes black.
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. Step 1
Read the threshold branch and its >=120 condition.
You should see: The boundary includes exactly 120 in the white class.
Thresholding maps the computed mean to black or white under a precise cutoff. This rule uses mean≥120 for white; below 120 becomes black.
2. Step 2
Calculate the primary-color mean 85 and apply the threshold.
You should see: Opaque primaries become black with alpha 255.
Thresholding maps the computed mean to black or white under a precise cutoff. This rule uses mean≥120 for white; below 120 becomes black.
3. Step 3
Inspect transparent white: mean 255 produces white RGB while alpha stays 0.
You should see: The transparent pixel remains transparent.
Thresholding maps the computed mean to black or white under a precise cutoff. This rule uses mean≥120 for white; below 120 becomes black.
4. Step 4
Record below/equal/above cutoff examples and run the threshold assertions.
You should see: A boundary/alpha threshold matrix.
Thresholding maps the computed mean to black or white under a precise cutoff. This rule uses mean≥120 for white; below 120 becomes black.
What to finish
Produce a below/equal/above threshold matrix with preserved alpha.
Watch for this
Leaving the equality boundary unspecified or changing alpha while claiming a color-only filter.
How can I tell I understand it?
Demonstrate the rule: Thresholding maps the computed mean to black or white under a precise cutoff. This rule uses mean≥120 for white; below 120 becomes black. Use the supplied variant to distinguish a changed result from a broken implementation.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
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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.
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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