oaustegard/processing-images

Image Processing Tools

This container has a rich image processing toolkit. Before writing any image code, scan this inventory to pick the best tool for the job — don't default to Pillow for everything.

Tool Selection by Task

Format Conversion & Batch Operations

ImageMagick convert is the default choice. Handles 260+ formats, single command, no code needed.

convert input.png output.webp
convert input.png -quality 85 output.jpg
mogrify -format webp *.png          # batch in-place

For animated formats (GIF↔WebP↔APNG, video↔frames), prefer ffmpeg.

Resize, Crop, Thumbnails

ImageMagick for CLI one-liners. Pillow when already in Python pipeline.

convert input.jpg -resize 800x600 output.jpg          # fit within box
convert input.jpg -resize 800x600^ -gravity center -extent 800x600 output.jpg  # fill+crop
convert input.jpg -thumbnail 200x200^ -gravity center -extent 200x200 thumb.jpg

IM supports 30+ resize filters: -filter Lanczos (sharp downscale), -filter Mitchell (balanced), -filter Point (nearest-neighbor/pixel art).

Compositing & Overlays

ImageMagick composite or convert with -composite. Supports all Porter-Duff modes.

composite -gravity southeast watermark.png photo.jpg output.jpg
convert base.png overlay.png -gravity center -composite result.png

For complex multi-layer work or programmatic positioning, use Pillow (Image.paste, Image.alpha_composite).

Montages, Collages, Contact Sheets

ImageMagick montage — purpose-built for grid layouts.

montage *.jpg -geometry 200x200+5+5 -tile 4x3 sheet.jpg
montage *.png -label '%f' -geometry +4+4 catalog.png

Animated GIFs & Frame Sequences

ImageMagick for simple GIF assembly. ffmpeg for anything involving timing control, video sources, or optimization.

convert -delay 10 -loop 0 frame_*.png animation.gif        # IM
ffmpeg -framerate 10 -i frame_%03d.png -vf palettegen palette.png && \
ffmpeg -framerate 10 -i frame_%03d.png -i palette.png -lavfi paletteuse output.gif  # optimized

imageio is convenient for frame-sequence GIFs from Python arrays.

Image Analysis & Measurement

identify for quick metadata and stats. OpenCV for structural analysis. scikit-image for scientific measurement.

identify -verbose image.png          # full metadata dump
identify -format '%wx%h %[colorspace] %[depth]bit' image.png   # targeted

• OpenCV (cv2): histograms, contour detection, template matching, edge detection, color distribution
• scikit-image (skimage): region properties, morphology, thresholding (Otsu, adaptive), feature detection (SIFT via OpenCV, ORB), SSIM comparison
• scipy.ndimage: convolution, interpolation, labeling connected components

Image Comparison & Diffing

ImageMagick compare produces visual diffs directly.

compare image1.png image2.png diff.png
compare -metric RMSE image1.png image2.png null: 2>&1   # numeric similarity

For structural similarity: skimage.metrics.structural_similarity (SSIM).

Color Operations

ImageMagick handles color space conversion, channel manipulation, color quantization.

convert input.jpg -colorspace Gray output.jpg
convert input.png -colors 16 reduced.png           # quantize
convert input.jpg -modulate 110,130,100 output.jpg  # brightness,saturation,hue
convert input.png -channel R -separate red_channel.png

For programmatic color analysis (dominant colors, palettes): OpenCV k-means on pixel arrays, or Pillow getcolors().

Effects & Filters

ImageMagick has extensive built-in effects:

convert in.png -blur 0x3 out.png              # Gaussian blur
convert in.png -sharpen 0x1 out.png
convert in.png -shadow 60x4+2+2 out.png       # drop shadow
convert in.png -vignette 0x40 out.png
convert in.png -sketch 0x10+120 out.png
convert in.png -charcoal 2 out.png
convert in.png -edge 1 out.png
convert in.png -emboss 1 out.png
convert in.png \( +clone -background black -shadow 60x4+0+0 \) +swap -background none -layers merge +repage rounded.png

For advanced/custom convolution kernels: scipy.ndimage or OpenCV.

Metadata & EXIF

identify -verbose reads all metadata. Pillow reads/writes EXIF programmatically.

identify -verbose image.jpg | grep -A20 'Properties:'

from PIL import Image
img = Image.open("photo.jpg")
exif = img.getexif()  # dict-like access to EXIF tags

Note: no exiftool in this container. Use identify or Pillow for metadata tasks.

Icons, Favicons, App Icons

ImageMagick generates multi-size ICO files directly.

convert icon.png -define icon:auto-resize=256,128,64,48,32,16 favicon.ico

For icon sets (iOS/Android), batch-resize with convert or mogrify to each required size.

PDF & EPS (limited)

ImageMagick can read/write PDF and EPS but Ghostscript is not installed — complex PDF rasterization may fail. For PDF-to-image, prefer Pillow (for simple cases), pdfplumber (text/table extraction), or the pdf skill (for full PDF manipulation). IM's built-in PDF delegate handles basic operations.

Seam Carving (Content-Aware Resize)

ImageMagick has Liquid Rescale (LQR) built in:

convert input.jpg -liquid-rescale 80x100%! output.jpg   # shrink width 20%, preserve content

SVG Handling

ImageMagick rasterizes SVG via its built-in delegate. For SVG→PNG at specific sizes:

convert -density 300 input.svg -resize 800x output.png

No Inkscape or rsvg-convert available. For SVG manipulation, work with the XML directly or use Python's lxml.

Complete Tool Inventory

| Tool | Type | Key Strength | |---|---|---| | ImageMagick 6.9 | CLI suite | 260 formats, effects, compositing, batch ops | | ffmpeg | CLI | Video/animation, frame extraction, optimized GIFs | | Graphviz | CLI | Diagram→image rendering (dot, neato, etc.) | | LibreOffice | CLI | Document→image conversion | | Pillow 12.1 | Python | General-purpose, EXIF, drawing, WebP/AVIF, freetype | | OpenCV 4.13 | Python | Computer vision, histograms, contours, morphology | | scikit-image 0.26 | Python | Scientific analysis, SSIM, segmentation, features | | Wand 0.6 | Python | Full ImageMagick API from Python | | imageio 2.37 | Python | Unified I/O, GIF frame sequences | | scipy.ndimage | Python | Convolution, interpolation, labeling | | numpy | Python | Raw pixel array math | | reportlab | Python | PDF generation with embedded images |

Key Constraints

• No Ghostscript — PDF/EPS rasterization is limited to IM's built-in delegate
• No potrace/autotrace — bitmap-to-vector tracing unavailable
• No standalone optimizers — no optipng, pngquant, jpegoptim, gifsicle (use IM quality settings or ffmpeg instead)
• No exiftool — use identify or Pillow for metadata
• No Inkscape — SVG manipulation is XML-level only
• HEIC/AVIF read-only in ImageMagick; Pillow supports AVIF read/write
• ImageMagick is v6 — use convert/identify commands, not magick (v7 syntax)