TEST LOG: how to make a thumbnail (Koldflux), 2026-10-24

1. Our sample thumbnails: drawn in code (SVG in headless Chromium, DejaVu Sans Bold), downscaled with ffmpeg lanczos.
Measured 2026-10-24 on VPS. ffmpeg 6.1.1-3ubuntu5, tesseract 5.3.4
OCR before at 1280x720 (upscaled 4x for OCR): [subscribe for more rides DAY 3 VLOG ]
OCR before at 360x202 (upscaled 4x for OCR): [subscribe for more rides DAY 3 VLOG ]
OCR before at 168x94 (upscaled 4x for OCR): []
OCR after at 1280x720 (upscaled 4x for OCR): [/ / y! RAIN y! / y/ RIDE y/ / / yl awa ]
OCR after at 360x202 (upscaled 4x for OCR): [RAIN R IDE ]
OCR after at 168x94 (upscaled 4x for OCR): [RAIN RIDE ]

2. Contrast and text height (WCAG 2.x relative luminance formula, from the colors we used):
before title text #e9eef0 vs sky at y=60 rgb(210,231,242): 1.09:1
before title text #e9eef0 vs sky at y=100 rgb(212,232,241): 1.08:1
before "DAY 3 VLOG" #f2f2f2 vs road #9a9a9a: 2.51:1
after RAIN #ffffff vs outline #0a1420: 18.52:1; vs sky #102236: 16.10:1
after RIDE #ffd23f vs outline #0a1420: 12.83:1; vs #1b3048: 9.30:1
text height at width 1280: before title 30 px font -> 30.0 px; after 190 px font -> 190.0 px (cap height about 0.73 of font size)
text height at width 360: before title 30 px font -> 8.4 px; after 190 px font -> 53.4 px (cap height about 0.73 of font size)
text height at width 168: before title 30 px font -> 3.9 px; after 190 px font -> 24.9 px (cap height about 0.73 of font size)

3. Live Koldflux tool, https://koldflux.com/tools/assets/youtube-video-thumbnail (Playwright, headless Chromium, 2026-10-24):
Tool run 2026-10-24T16:28:49Z against live https://koldflux.com/tools/assets/youtube-video-thumbnail
=== A good thumbnail (thumb-after-1280x720.png)
Check input image Apply crop and recheck PNG Reset result Output checked and ready. Download measured-image.png Output checks {   "inputWidth": 1280,   "inputHeight": 720,   "inputBytes": 93531,   "inputFormat": "PNG",   "width": 1280,   "height": 720,   "outputBytes": 162254,   "format": "PNG",   "rgba": [     101,     121,     143,     255   ],   "hex": "#65798f",   "memoryEnvelopeBytes": 30694070,   "inputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uploadDevice": "mobile",     "maxBytes": 2000000   },   "scope": "Image pixels only. Animation and metadata are not retained in a PNG
--- after apply: Apply crop and recheck PNG Reset result Output checked and ready. Download resized-image.png Output checks {   "inputWidth": 1280,   "inputHeight": 720,   "inputBytes": 93531,   "inputFormat": "PNG",   "width": 3840,   "height": 2160,   "outputBytes": 1337643,   "format": "PNG",   "memoryEnvelopeBytes": 119167670,   "inputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uploadDevice": "mobile",     "maxBytes": 2000000   },   "outputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uploa
=== A square image (square-1080.png, pad)
Check input image Apply pad and recheck PNG Reset result Output checked and ready. Download measured-image.png Output checks {   "inputWidth": 1080,   "inputHeight": 1080,   "inputBytes": 207993,   "inputFormat": "PNG",   "width": 1080,   "height": 1080,   "outputBytes": 352678,   "format": "PNG",   "rgba": [     16,     34,     54,     255   ],   "hex": "#102236",   "memoryEnvelopeBytes": 36798194,   "inputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uploadDevice": "mobile",     "maxBytes": 2000000   },   "scope": "Image pixels only. Animation and metadata are not retained in a PNG 
--- after apply: Apply pad and recheck PNG Reset result Output checked and ready. Download resized-image.png Output checks {   "inputWidth": 1080,   "inputHeight": 1080,   "inputBytes": 207993,   "inputFormat": "PNG",   "width": 3840,   "height": 2160,   "outputBytes": 1157331,   "format": "PNG",   "memoryEnvelopeBytes": 122334194,   "inputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uploadDevice": "mobile",     "maxBytes": 2000000   },   "outputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uplo
=== A square image crop (square-1080.png, crop)
Check input image Apply crop and recheck PNG Reset result Output checked and ready. Download measured-image.png Output checks {   "inputWidth": 1080,   "inputHeight": 1080,   "inputBytes": 207993,   "inputFormat": "PNG",   "width": 1080,   "height": 1080,   "outputBytes": 352678,   "format": "PNG",   "rgba": [     16,     34,     54,     255   ],   "hex": "#102236",   "memoryEnvelopeBytes": 36798194,   "inputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uploadDevice": "mobile",     "maxBytes": 2000000   },   "scope": "Image pixels only. Animation and metadata are not retained in a PNG
--- after apply: Apply crop and recheck PNG Reset result Output checked and ready. Download resized-image.png Output checks {   "inputWidth": 1080,   "inputHeight": 1080,   "inputBytes": 207993,   "inputFormat": "PNG",   "width": 3840,   "height": 2160,   "outputBytes": 1603058,   "format": "PNG",   "memoryEnvelopeBytes": 122334194,   "inputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "uploadDevice": "mobile",     "maxBytes": 2000000   },   "outputChecks": {     "sourceStatus": "UNKNOWN - source review overdue",     "minimumWidth": "UNKNOWN",     "minimumHeight": "UNKNOWN",     "byteLimit": "UNKNOWN",     "allowedFormat": "UNKNOWN",     "recommendedCanvas": "UNKNOWN - source review overdue",     "accountAcceptance": "UNKNOWN - local checks cannot verify your account or a platform upload",     "upl

4. Updated thumbnail tool, local build of koldflux:hubos candidate, 2026-10-26 (Playwright, headless Chromium, device Mobile, byte limit 2,000,000 shown by the tool). The source review was redone on 2026-10-25 (see tool-limit-check-log.txt).
thumb-after-1280x720.png: input 93,531 B PNG; minimumWidth PASS; byteLimit PASS; allowedFormat PASS; recommendedCanvas ADVISORY - differs from recommendation; accountAcceptance UNKNOWN (cannot be verified locally, by design).
thumb-before-1280x720.png: input 62,474 B PNG; minimumWidth PASS; byteLimit PASS; allowedFormat PASS; recommendedCanvas ADVISORY - differs from recommendation; accountAcceptance UNKNOWN (cannot be verified locally, by design).