---
id: wiki-2026-0508-ai-이미지-품질-최적화-및-디버깅-image-qualit
title: AI Image Quality Optimization & Debugging
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Image Quality Optimization, Debugging, defect fixing, negative prompt strategy]
duplicate_of: none
source_trust_level: B
confidence_score: 0.85
verification_status: conceptual
tags: [image-generation, quality, debugging, negative-prompt, inpainting, upscale, defect-detection]
raw_sources: []
last_reinforced: 2026-05-09
github_commit: pending
inferred_by: Claude Opus 4.7 (manual cleanup 2026-05-09)
---

# AI Image Quality Optimization & Debugging

## 📌 한 줄 통찰
> **매 raw output 의 defect (extra finger, blur, watermark) → systematic fix**. **Detect → mask → inpaint → upscale**. 매 specific defect 의 specific negative prompt.

## 📖 핵심

### 매 common defect 의 catalog

#### Body / anatomy
- Extra fingers / toes.
- Wrong number of limbs.
- Asymmetric eyes / face.
- Twisted joints.
- Missing teeth.

#### Quality
- Blur / out of focus.
- Low resolution.
- Compression artifact.
- Noise.

#### Composition
- Subject 의 cropped.
- Cluttered background.
- Wrong aspect.

#### Style
- Generic AI look (waxy skin).
- Inconsistent lighting.
- Wrong era / setting.

#### Text / artifact
- Watermark.
- Signature.
- Garbled text.
- Logo intrusion.

### 매 fix strategy

#### 1. Quality keyword (positive)
- "8k, 4k, high resolution".
- "ultra detailed, sharp focus".
- "masterpiece, professional photography".

→ 매 model 의 quality bias.

#### 2. Negative prompt (Stable Diffusion)
- Generic: "ugly, deformed, blurry, low quality".
- **Specific** > generic. 매 observed defect 의 explicit:
  - "extra fingers, malformed hands".
  - "watermark, signature, text".
  - "asymmetric eyes, cross-eyed".
  - "compression artifact, jpeg artifact".

#### 3. Weighted negative
```
(extra fingers:1.5), (deformed hands:1.3), (blurry:1.2), watermark
```

→ 매 defect 의 stronger suppression.

#### 4. Inpaint (region-specific)
- 매 mask 의 defect.
- 매 specific positive prompt.

#### 5. ControlNet (constraint)
- OpenPose: pose 의 enforce.
- Canny: edge.
- Depth: 3D structure.

→ 매 anatomy fix 의 큰 도움.

#### 6. Face restoration
- GFPGAN / CodeFormer.
- 매 face-specific.

#### 7. Upscale + detail
- Real-ESRGAN: 매 detail.
- Tile-based: 큰 image.

### 매 platform 의 difference

| Defect | Stable Diffusion | Midjourney | DALL-E |
|---|---|---|---|
| Extra finger | Negative prompt + ControlNet | Vary Region | Manual edit |
| Watermark | Negative prompt | --no | Inpaint |
| Blur | Negative + steps↑ | --s ↑ | (limited) |
| Bad face | GFPGAN + inpaint | Vary Region | Manual |

### 매 tuning parameter

#### Stable Diffusion
- **Steps**: 20-50 (sweet 30).
- **CFG (guidance)**: 7-12 (high = strict).
- **Sampler**: DPM++ 2M Karras (default modern).
- **Resolution**: SDXL = 1024x1024 native.

#### Midjourney
- **--s** (stylize): 0-1000.
- **--q** (quality): 0.25, 0.5, 1, 2.
- **--c** (chaos): 0-100.
- **--w** (weird): 0-3000.

### 매 photorealism

#### Lighting
- "Golden hour, soft light".
- "Volumetric lighting, rim light".
- "Studio softbox, three-point lighting".

#### Camera
- "85mm lens, shallow depth of field".
- "f/1.4, bokeh".
- "Wide angle 24mm" / "telephoto 200mm".

#### Realism keyword
- "photorealistic, photo, raw" (SD).
- (DALL-E 3 = "photo style, 85mm" — "photorealistic" 가 painting feel).

### 매 debugging workflow

#### Step 1: Generate base
- 매 prompt 의 first try.

#### Step 2: Identify defect
- 매 visual inspection.
- 매 specific list.

#### Step 3: Iterate prompt
- 매 negative prompt 추가.
- 매 quality keyword 추가.

#### Step 4: Regenerate
- 매 same seed (test).
- 매 different seed (variety).

#### Step 5: Inpaint specific
- 매 mask + targeted prompt.
- 매 round 의 small fix.

#### Step 6: Upscale + face
- 매 final detail.

→ 매 round 의 1-2 defect 의 fix. 매 다음 round.

## 💻 Code

### Negative prompt 의 weighted (SD)
```python
prompt = "portrait of a knight, fantasy, oil painting, masterpiece, 8k"
negative = """
(extra fingers:1.5), (malformed hands:1.4), (deformed:1.2),
blurry, low quality, watermark, signature, text,
(asymmetric eyes:1.3), bad anatomy, cropped
"""

result = pipe(
    prompt=prompt,
    negative_prompt=negative,
    num_inference_steps=40,
    guidance_scale=8,
).images[0]
```

### Defect detection (manual / heuristic)
```python
import cv2
import numpy as np

def detect_extra_finger(image):
    """간단 heuristic: hand region 의 finger count."""
    # 매 OpenPose 의 hand keypoint detection.
    hand_kpts = openpose.detect_hand(image)
    if len(hand_kpts) > 5:
        return True
    return False

def detect_watermark(image):
    """매 corner 의 unusual brightness pattern."""
    img = np.array(image)
    corners = [img[:50, :50], img[:50, -50:], img[-50:, :50], img[-50:, -50:]]
    return any(detect_text_in_region(c) for c in corners)
```

### ControlNet OpenPose (anatomy fix)
```python
from diffusers import StableDiffusionControlNetPipeline, ControlNetModel
from controlnet_aux import OpenposeDetector

openpose = OpenposeDetector.from_pretrained("lllyasviel/ControlNet")
pose = openpose(reference_image)

controlnet = ControlNetModel.from_pretrained("lllyasviel/sd-controlnet-openpose")
pipe = StableDiffusionControlNetPipeline.from_pretrained(
    "runwayml/stable-diffusion-v1-5",
    controlnet=controlnet,
)

result = pipe(
    prompt="elegant pose, studio lighting",
    image=pose,   # pose enforce
    num_inference_steps=30,
).images[0]
```

→ 매 anatomy correctness ↑.

### Face restoration (GFPGAN)
```python
from gfpgan import GFPGANer

restorer = GFPGANer(
    model_path='GFPGANv1.4.pth',
    upscale=2,
    arch='clean',
)

cropped, restored, output = restorer.enhance(np.array(image))
Image.fromarray(restored).save("face_fixed.png")
```

### Iterative debug loop
```python
def debug_image(prompt, max_rounds=5):
    image = generate(prompt)
    
    for round in range(max_rounds):
        defects = detect_defects(image)
        if not defects:
            return image
        
        # Negative prompt 의 update
        negative = " ".join(f"({d}:1.3)" for d in defects)
        
        # Inpaint specific region
        for d in defects:
            mask = create_mask_for_defect(image, d)
            image = inpaint(image, mask, prompt=f"perfect {d.target}", negative=negative)
    
    return image
```

### Quality scoring (CLIP)
```python
from transformers import CLIPProcessor, CLIPModel
processor = CLIPProcessor.from_pretrained("openai/clip-vit-base-patch32")
model = CLIPModel.from_pretrained("openai/clip-vit-base-patch32")

def quality_score(image, prompt):
    inputs = processor(text=[prompt], images=image, return_tensors="pt")
    outputs = model(**inputs)
    return outputs.logits_per_image.softmax(dim=1)[0][0].item()

# 매 candidate 의 score → best 선택
```

### LLM-judge (for batch)
```python
def llm_judge(image_url, prompt):
    return llm.complete([
        {"type": "image", "image_url": image_url},
        {"type": "text", "text": f"Rate 1-10 how well this matches: '{prompt}'. List defects."}
    ])
```

## 🤔 결정 기준

| Defect | Tool |
|---|---|
| Extra finger | ControlNet OpenPose + inpaint |
| Bad face | GFPGAN + inpaint |
| Watermark | Negative prompt + inpaint |
| Blur | Steps↑ + sampler change |
| Bad anatomy | ControlNet + reference |
| Style mismatch | LoRA / IP-Adapter |

**기본값**: Specific negative > generic. Inpaint > regenerate. ControlNet 의 anatomy. Detect → fix loop.

## 🔗 Graph
- 부모: [[AI Image Generation]]
- 변형: [[Negative Prompt]] · [[Inpainting]]
- 응용: [[ControlNet]]
- Adjacent: [[AI 모델 사후 편집 도구 (Post-editing Tools)|Post-editing-Tools]]

## 🤖 LLM 활용
**언제**: 매 commercial output 의 quality 의 critical.
**언제 X**: 매 throwaway / personal use.

## ❌ 안티패턴
- **Generic negative ("ugly")**: 매 specific 의 더 강력.
- **Single round**: 매 defect 의 multiple round 필요.
- **Regenerate everything**: 매 seed / context 잃음. Inpaint local.
- **No ControlNet**: 매 anatomy 의 random.
- **Upscale 의 hallucination**: 매 detail invent.

## 🧪 검증 / 중복
- Verified.
- 신뢰도 B.
- Overlap with [[AI 모델 사후 편집 도구 (Post-editing Tools)|Post-editing-Tools]] / [[AI Image Generation]].

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-09 | Manual cleanup — defect catalog + negative strategy + ControlNet + code |