Add resistor/capacitor/SMD value calculator with component image generation

[Sebbeben]

Why

I often order component assortments — resistor and capacitor kits — from AliExpress. They show up as a big box of values, and when I import them into Part-DB it's honestly a bit sad to see rows of blank thumbnails with almost no information. So I built a tool that draws a clean, consistent picture for each passive component straight from its value, and can illustrate a whole assortment in one go.

What it does

Value calculator (Tools → Value calculator) — interactively draw a:

• resistor as colour bands (4/5/6 band; tolerance, power and temperature-coefficient reflected),
• SMD resistor with the 3-digit / 4-digit / EIA-96 marking for its package,
• ceramic capacitor as a radial disc or MLCC blob (printed code, voltage line, tolerance letter).

Value ⇄ code ⇄ bands are bidirectionally linked and the picture redraws live. Output is a transparent SVG, so it stays crisp at any size.

Generate on a part — a part with no picture shows a Generate image button in the picture area that opens the calculator pre-filled from the part's value; attach it without leaving the page.

Bulk "Generate component images" — a parts-table action that classifies the selected parts, reads their value and properties (from parameters, else the name/description), and shows a review table with a live preview per part. From there you can attach the pictures and/or write suggested KiCad symbol / footprint / reference to the parts. Only parts without a picture are listed; an overwrite mode can re-generate ones that already have a (generated) picture.

Detection follows real-world conventions: capacitor tolerance → code letter (104K), through-hole resistor tolerance/ppm → colour bands, SMD resistor tolerance → 3- vs 4-digit code, power → resistor body size, etc.

Implementation notes

• New ComponentValueGuesser service classifies a part and parses value / tolerance / voltage / power / ppm / pitch / diameter / body-colour / SMD-package from parameters or free text (name/description), and suggests a KiCad symbol + footprint.
• New GeneratedImageAttachmentHelper stores the SVG as a picture attachment through the existing upload pipeline (so the SVG is sanitized), optionally replacing a previous generated image — manually uploaded pictures are never removed.
• All drawing is client-side in a Stimulus controller (no server-side image libraries). The bulk previews reuse the exact same drawing code via a hidden calculator instance.
• The generate_image and set_eda endpoints require edit on the part plus a per-part CSRF token; the tool sits behind a new @tools.value_calculator permission.
• Unit tests for ComponentValueGuesser; usage docs at docs/usage/component_image_generator.md.

The generated images are illustrations (code/bands + dimension callouts), not photographs.

Screenshots

Value calculator (resistor / SMD / capacitor tabs)

"How to get the most auto-filled" help panel

Bulk action in the parts table

Bulk review with live previews

Testing

• ComponentValueGuesserTest covers value parsing (including the kΩ/MΩ cases), classification, and the property/EDA detection.
• Manually tested end-to-end (single-part generate + bulk generate) for resistors, SMD resistors and ceramic capacitors.

[codecov]

Codecov Report

❌ Patch coverage is 80.83538% with 78 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.86%. Comparing base (7244803) to head (9ebf399).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Services/Tools/ComponentValueGuesser.php	81.98%	40 Missing ⚠️
...ces/Attachments/GeneratedImageAttachmentHelper.php	70.45%	13 Missing ⚠️
src/Controller/PartController.php	76.08%	11 Missing ⚠️
src/Controller/ToolsController.php	90.24%	8 Missing ⚠️
src/Services/Parts/PartsTableActionHandler.php	14.28%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1435      +/-   ##
============================================
+ Coverage     58.49%   58.86%   +0.36%     
- Complexity     8701     8856     +155     
============================================
  Files           638      640       +2     
  Lines         28123    28530     +407     
============================================
+ Hits          16451    16793     +342     
- Misses        11672    11737      +65     

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