From fb3952d54f96315a2fa77405a81ac59ef1e10d30 Mon Sep 17 00:00:00 2001
From: altair823 <dlsrks0734@gmail.com>
Date: Wed, 27 May 2026 05:36:56 +0000
Subject: [PATCH] docs(pdf-ocr): correct F7 conversion engine record in PoC doc
 (gs, not ImageMagick)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

aeeff36 의 PoC doc append (engine-comparison.md L134, L141) 가 F7 (`ccitt.pdf`)
의 conversion engine 을 "ImageMagick `convert -compress Group4`" 로 기록했으나,
실제 tests/fixtures/_synth/flate_ccittfax.sh:77-83 은
`gs -sDEVICE=pdfwrite -dMonoImageFilter=/CCITTFaxEncode -dEncodeMonoImages=true`
flag 사용 (ImageMagick `convert` 호출 0회).

fixture binary (`/Filter [ /CCITTFaxDecode ]`, 2060 bytes) 는 invariant 충족 OK
(Step 2 spec compliance + code quality review verified). historical record 의
factual correction only.

review trail:
- impl result: .omc/reviews/2026-05-27-pdf-ocr-step-02-impl-result.md
- spec review: .omc/reviews/2026-05-27-pdf-ocr-step-02-spec-review-result.md
- code review: .omc/reviews/2026-05-27-pdf-ocr-step-02-code-review-result.md (I1)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 docs/superpowers/poc/2026-05-27-pdf-ocr-engine-comparison.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/superpowers/poc/2026-05-27-pdf-ocr-engine-comparison.md b/docs/superpowers/poc/2026-05-27-pdf-ocr-engine-comparison.md
index 43aa8f4..102da82 100644
--- a/docs/superpowers/poc/2026-05-27-pdf-ocr-engine-comparison.md
+++ b/docs/superpowers/poc/2026-05-27-pdf-ocr-engine-comparison.md
@@ -131,11 +131,11 @@ B2 fixture 합성 후 actual `/Filter` 측정 (shell grep + Python re 기반 pro
 - F6 (`flate_raw.pdf`): `/Filter /FlateDecode` — 872 bytes, DCTDecode 부재 ✅.
   Pillow RGB→PDF 가 DCTDecode 를 사용하는 것 확인 → 수동 PDF 작성(zlib.compress) 으로 생성.
 - F7 (`ccitt.pdf`): `/Filter [ /CCITTFaxDecode ]` — 2060 bytes, DCTDecode 부재 ✅.
-  Pillow bilevel('1') + TIFF group4 → ImageMagick `convert -compress Group4` 경로.
+  Pillow bilevel('1') + TIFF group4 → ghostscript `pdfwrite -dMonoImageFilter=/CCITTFaxEncode -dEncodeMonoImages=true` 경로.
 
 Step 3 의 `extract_dctdecode_page_image` 의 baseline.
 
 주요 관찰:
 - reportlab 기본값 (`useA85=1`) 은 `/Filter [ /ASCII85Decode /DCTDecode ]` chain → `useA85=0` 으로 순수 DCTDecode 획득.
 - Pillow `Image.new('RGB').save('.pdf','PDF')` 는 DCTDecode (JPEG) 로 저장 — FlateDecode raw pixel 이 필요한 F6 는 수동 PDF 작성 필요.
-- ghostscript pdfwrite 가 TIFF 직접 입력을 지원 안 함 (v10.02.1 `/undefined in II*`) — ImageMagick `convert -compress Group4` 로 대체.
+- ghostscript pdfwrite default 가 TIFF 입력 시 `/undefined in II*` 로 실패 — `-dMonoImageFilter=/CCITTFaxEncode -dEncodeMonoImages=true` flag 로 우회 (ImageMagick fallback 불필요).