渲染出版圖形

製作合學術期刊、書籍、簡報與網路出版技術需求之發布級圖形。涵蓋 DPI 需求、色空間管理、排版最佳實踐、文件格式選擇與元資料嵌入。

適用時機

• 為學術期刊投稿備圖
• 為印刷出版（書、雜誌）建圖
• 為簡報生高品質資產
• 為網路出版以適當優化匯出視覺化
• 確圖形合出版者技術規範
• 帶適當元資料歸檔圖形
• 自單一源建多格式匯出

輸入

步驟

1. 定輸出需求

辨識目標出版之技術規範：

# Common publication requirements

academic_journal:
  dpi: 300-600
  format: TIFF, EPS, PDF
  color_space: RGB or CMYK (check guidelines)
  max_width: 180mm (single column) or 390mm (double column)
  fonts: Embed or outline
  resolution_minimums:
    line_art: 1000 DPI
    halftone: 300 DPI
    combination: 600 DPI

web_publication:
  dpi: 72-96 (retina: 144-192)
  format: PNG, WebP, SVG
  color_space: sRGB
  max_file_size: 200KB-500KB
  optimization: Compress, progressive loading

presentation:
  dpi: 96-150
  format: PNG, PDF, SVG
  color_space: RGB
  dimensions: 16:9 or 4:3 aspect ratio
  contrast: High contrast for projectors

print_book:
  dpi: 300-600
  format: TIFF, PDF/X
  color_space: CMYK
  bleed: 3-5mm beyond trim
  fonts: Embedded

預期： 對目標需求有明確理解 失敗時： 聯繫出版者問特定指南，用保守預設

2. 為點陣圖形設正確 DPI

依輸出媒體配置解析度：

from PIL import Image

def set_dpi_pillow(image_path, output_path, target_dpi=300):
    """Set DPI metadata for PNG/TIFF."""
    img = Image.open(image_path)

    # Save with DPI metadata
    img.save(output_path, dpi=(target_dpi, target_dpi))
    print(f"Saved with {target_dpi} DPI: {output_path}")

def calculate_dimensions(width_mm, height_mm, dpi=300):
    """Calculate pixel dimensions from physical size."""
    # Convert mm to inches
    width_inches = width_mm / 25.4
    height_inches = height_mm / 25.4

    # Calculate pixels
    width_px = int(width_inches * dpi)
    height_px = int(height_inches * dpi)

    return width_px, height_px

# Example: 180mm wide figure at 300 DPI
width, height = calculate_dimensions(180, 120, dpi=300)
print(f"Required resolution: {width}x{height} pixels")
# Output: Required resolution: 2126x1417 pixels

# R ggplot2 export with proper DPI
library(ggplot2)

# Create plot
p <- ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point() +
  theme_minimal(base_size = 12)

# Save for publication (300 DPI)
ggsave(
  filename = "figure1.png",
  plot = p,
  width = 180,
  height = 120,
  units = "mm",
  dpi = 300
)

# Save as vector for flexibility
ggsave(
  filename = "figure1.pdf",
  plot = p,
  width = 180,
  height = 120,
  units = "mm",
  device = cairo_pdf  # Better text rendering
)

預期： 圖形以印刷品質之正確解析度渲染 失敗時： 驗 DPI 元資料正確存入，檢文件大小適當

3. 配置色空間

設適當之色彩設定檔：

from PIL import Image, ImageCms

def convert_to_cmyk(rgb_image_path, cmyk_output_path):
    """Convert RGB to CMYK for print."""
    img = Image.open(rgb_image_path)

    if img.mode != 'RGB':
        img = img.convert('RGB')

    # Convert to CMYK
    cmyk_img = img.convert('CMYK')
    cmyk_img.save(cmyk_output_path, format='TIFF', compression='tiff_lzw')
    print(f"Converted to CMYK: {cmyk_output_path}")

def apply_srgb_profile(image_path, output_path):
    """Apply sRGB profile for web."""
    img = Image.open(image_path)

    # sRGB profile (embedded in Pillow)
    srgb_profile = ImageCms.createProfile('sRGB')

    # Convert to sRGB
    img_srgb = ImageCms.profileToProfile(
        img,
        srgb_profile,
        srgb_profile,
        renderingIntent=ImageCms.Intent.PERCEPTUAL
    )

    img_srgb.save(output_path)

# ImageMagick for color space conversion
convert input.png -colorspace sRGB output_srgb.png
convert input.png -colorspace CMYK output_cmyk.tiff

# Check color profile
identify -verbose image.png | grep -i colorspace

預期： 色空間合出版需求 失敗時： 驗色彩設定檔已嵌，試印預覽

4. 配置排版

確保文字可讀且格式得當：

from PIL import ImageFont

def get_publication_fonts():
    """Load fonts appropriate for publication."""
    # Common publication-safe fonts
    fonts = {
        'serif': 'Times New Roman',
        'sans': 'Arial',
        'mono': 'Courier New'
    }

    try:
        # Load with proper size for DPI
        # At 300 DPI, 12pt = 12 * 300/72 = 50 pixels
        base_size_300dpi = 50

        font_regular = ImageFont.truetype(f"{fonts['sans']}.ttf", base_size_300dpi)
        font_bold = ImageFont.truetype(f"{fonts['sans']} Bold.ttf", base_size_300dpi)

        return {'regular': font_regular, 'bold': font_bold}
    except:
        return {'regular': ImageFont.load_default(), 'bold': ImageFont.load_default()}

# Typography guidelines
typography_specs = {
    'minimum_font_size': '8pt',  # Readable when printed
    'line_width_min': 0.5,  # Points, for print clarity
    'panel_labels': {
        'font': 'Arial Bold',
        'size': '12pt',
        'position': 'top-left',
        'style': 'A, B, C'  # Or (a), (b), (c)
    },
    'axis_labels': {
        'font': 'Arial',
        'size': '10pt'
    },
    'legend': {
        'font': 'Arial',
        'size': '9pt',
        'position': 'outside plot area'
    }
}

# R publication-quality typography
library(ggplot2)

p <- ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point(size = 2) +
  labs(
    title = "Fuel Efficiency vs Weight",
    x = "Weight (1000 lbs)",
    y = "Miles per Gallon"
  ) +
  theme_bw(base_size = 12, base_family = "Arial") +
  theme(
    plot.title = element_text(size = 14, face = "bold"),
    axis.title = element_text(size = 12),
    axis.text = element_text(size = 10),
    legend.text = element_text(size = 10),
    panel.grid.minor = element_blank(),
    # Ensure text is black for print
    text = element_text(color = "black")
  )

預期： 文字於出版尺寸下可讀，字體正確嵌入 失敗時： 增大字號，檢字體授權，將文字轉為輪廓

5. 選適當之文件格式

依用例擇格式：

def export_multi_format(source_path, output_base, formats=['png', 'pdf', 'tiff']):
    """Export graphic in multiple formats."""
    from PIL import Image
    import cairosvg
    import os

    base, ext = os.path.splitext(output_base)

    if ext.lower() in ['.svg']:
        # SVG source - convert to rasters
        for fmt in formats:
            output = f"{base}.{fmt}"

            if fmt == 'png':
                cairosvg.svg2png(
                    url=source_path,
                    write_to=output,
                    output_width=2126,  # 180mm @ 300 DPI
                    output_height=1417   # 120mm @ 300 DPI
                )
            elif fmt == 'pdf':
                cairosvg.svg2pdf(url=source_path, write_to=output)
            elif fmt == 'tiff':
                # Convert via PNG intermediate
                temp_png = f"{base}_temp.png"
                cairosvg.svg2png(url=source_path, write_to=temp_png)
                img = Image.open(temp_png)
                img.save(output, format='TIFF', compression='tiff_lzw')
                os.remove(temp_png)

    else:
        # Raster source
        img = Image.open(source_path)

        for fmt in formats:
            output = f"{base}.{fmt}"

            if fmt == 'png':
                img.save(output, format='PNG', dpi=(300, 300), optimize=True)
            elif fmt == 'tiff':
                img.save(output, format='TIFF', compression='tiff_lzw', dpi=(300, 300))
            elif fmt == 'pdf':
                # Use img2pdf or similar for raster-to-PDF
                img.save(output, format='PDF', resolution=300.0)

    print(f"Exported in formats: {', '.join(formats)}")

# Format selection guide
format_guide = {
    'TIFF': {
        'use_for': 'Journal submission, archival',
        'benefits': 'Lossless, supports CMYK, high quality',
        'compression': 'LZW or ZIP (lossless)'
    },
    'PDF': {
        'use_for': 'Submission, print, archival',
        'benefits': 'Vector or raster, text searchable, widely accepted',
        'variants': 'PDF/A (archival), PDF/X (print)'
    },
    'PNG': {
        'use_for': 'Web, presentations, digital',
        'benefits': 'Lossless, transparency, good compression',
        'limitation': 'RGB only, larger than JPEG'
    },
    'SVG': {
        'use_for': 'Web, further editing, scalable graphics',
        'benefits': 'Vector, infinitely scalable, small file size',
        'limitation': 'Not always accepted by journals'
    },
    'EPS': {
        'use_for': 'Legacy journal requirements',
        'benefits': 'Vector format accepted by older systems',
        'limitation': 'Being phased out, use PDF instead'
    }
}

預期： 適合出版渠道之格式 失敗時： 檢出版者要求，提供多種格式

6. 為網路優化

建網路優化版本：

def optimize_for_web(input_path, output_path, max_width=1200, quality=85):
    """Optimize image for web publication."""
    from PIL import Image

    img = Image.open(input_path)

    # Resize if too large
    if img.width > max_width:
        ratio = max_width / img.width
        new_height = int(img.height * ratio)
        img = img.resize((max_width, new_height), Image.LANCZOS)

    # Convert to RGB if needed
    if img.mode in ('RGBA', 'LA', 'P'):
        background = Image.new('RGB', img.size, (255, 255, 255))
        if img.mode == 'P':
            img = img.convert('RGBA')
        background.paste(img, mask=img.split()[-1] if 'A' in img.mode else None)
        img = background

    # Save optimized
    img.save(output_path, format='JPEG', quality=quality, optimize=True, progressive=True)

    # Check file size
    import os
    file_size_kb = os.path.getsize(output_path) / 1024
    print(f"Optimized: {file_size_kb:.1f} KB")

def create_responsive_set(input_path, output_base):
    """Create multiple resolutions for responsive web."""
    from PIL import Image

    img = Image.open(input_path)
    sizes = [
        (640, '640w'),
        (1024, '1024w'),
        (1920, '1920w')
    ]

    for width, suffix in sizes:
        if img.width >= width:
            ratio = width / img.width
            height = int(img.height * ratio)
            resized = img.resize((width, height), Image.LANCZOS)

            output = f"{output_base}_{suffix}.jpg"
            resized.save(output, format='JPEG', quality=85, optimize=True)

預期： 網路優化圖像於 500KB 下，已生響應式尺寸 失敗時： 降品質、再縮小、考慮 WebP 格式

7. 嵌入元資料

加描述性元資料以資歸檔：

from PIL import Image
from PIL.PngImagePlugin import PngInfo

def embed_metadata(image_path, output_path, metadata):
    """Embed metadata in PNG."""
    img = Image.open(image_path)

    # Create metadata
    png_info = PngInfo()
    for key, value in metadata.items():
        png_info.add_text(key, str(value))

    # Save with metadata
    img.save(output_path, format='PNG', pnginfo=png_info)

# Example metadata
metadata = {
    'Title': 'Figure 1: Relationship between weight and fuel efficiency',
    'Author': 'Jane Doe',
    'Description': 'Scatter plot showing negative correlation',
    'Copyright': 'CC-BY 4.0',
    'Software': 'R 4.3.0, ggplot2 3.4.0',
    'Creation Date': '2026-02-16',
    'Source': 'mtcars dataset'
}

embed_metadata('figure1.png', 'figure1_with_metadata.png', metadata)

預期： 元資料已嵌且可取 失敗時： 檢格式支援元資料（PNG、TIFF、PDF 是；JPEG 受限）

驗證

• DPI 合出版需求（典型 300+）
• 物理尺寸合出版正確
• 色空間適當（網用 RGB，印用 CMYK）
• 文件格式為出版者所受
• 文字於出版尺寸下可讀
• 字體已嵌或輪廓化
• 線寬印時可見
• 灰階印之色對比足
• 文件大小於限內
• 元資料已嵌
• 已測印預覽或渲染

常見陷阱

1. 解析度不足：72 DPI 網路圖形無法以品質印刷
2. 錯之色空間：RGB 圖形印之或異於顯示
3. 字體替換：未嵌之字體被預設替換
4. 文字過小：8pt 下之字體印之或不可讀
5. 線過細：0.5pt 下之線印之或不清
6. 文件大小：高 DPI 圖形可能極大，宜適當壓縮
7. 壓縮偽影：JPEG 壓縮不宜用於線稿或文字
8. 缺出血：印刷圖形需 3-5mm 出血外於裁切
9. 透明問題：某些格式不能正確保留透明
10. 寬高比：尺寸計算錯致變形

相關技能

• create-2d-composition：建源圖形
• render-blender-output：出版用之 3D 渲染設定
• generate-quarto-report：將圖形整合入文件