Web Image Optimizer

Automates the full pipeline of preparing images for web use: convert, rename, resize, and compress.

Prerequisites

• ImageMagick must be installed (brew install imagemagick on macOS)
• Verify with: which magick

The Pipeline

When the user asks to optimize images, follow these steps in order:

1. Scan the source folder

List all images and show a summary:

• Total number of images found
• Formats present (JPG, HEIC, PNG, TIFF, etc.)
• Total size
• Size range (smallest to largest)

Supported formats: .jpg, .jpeg, .png, .heic, .heif, .tiff, .tif, .webp, .bmp

2. Ask the user for preferences (if not already provided)

• Source folder: where the original images are
• Naming prefix: e.g., project-photos → produces project-photos-1.jpg, project-photos-2.jpg, etc.
• Starting number: default is 1, but if the user already has photos numbered 1-22, start at 23

3. Create output folder

Never modify originals. Create a sibling folder named <source>-optimized/.

Example: more-photos/ → more-photos-optimized/

4. Process each image

For each image, run this ImageMagick command:

magick "<input>" -auto-orient -strip -resize <resize> -quality <quality> -sampling-factor 4:2:0 -colorspace sRGB "<output>.jpg"

Resize rules:

• If width > height (horizontal): -resize 1250x (max 1250px width, height scales proportionally)
• If height >= width (vertical): -resize x1250 (max 1250px height, width scales proportionally)
• If already within limits: no resize needed

Compression strategy:

• Start at quality 82
• Check file size after conversion
• If > 400KB, reduce quality by 5 and re-convert
• Repeat until ≤ 400KB or quality reaches 50 (never go below 50)
• Target is ~300KB per image

Flags explained:

• -auto-orient: fix rotation from EXIF data
• -strip: remove all metadata (EXIF, GPS, etc.) — reduces size and improves privacy
• -sampling-factor 4:2:0: chroma subsampling, standard for web JPEGs
• -colorspace sRGB: ensure consistent color across browsers

5. Show results

After processing, display a summary table:

Original Name              → New Name                    Size    Reduction
IMG_8242.jpg               → project-photos-1.jpg   285KB   -72%
IMG_5660.HEIC              → project-photos-2.jpg   198KB   -87%
...

And totals:

• Images processed: X / Y
• Total size before: XXX MB
• Total size after: XX MB
• Overall reduction: XX%

6. Offer next steps

• Ask if the user wants to move the optimized images to a specific folder
• Ask if the originals can be deleted (never delete without explicit confirmation)
• If images from other folders also need processing, offer to repeat

Important Notes

• Write a temporary bash script (e.g., _process.sh) to do the processing, then delete it after. This avoids quoting issues with inline bash loops.
• Use #!/bin/bash (not zsh) — zsh on macOS lacks mapfile. Use while IFS= read -r -d '' f with find -print0 to handle filenames with spaces, accents, or special characters safely.
• Always quote file paths with double quotes — filenames may have spaces, accents (e.g., "Cópia de"), or leading spaces.
• Always show progress: [1/33] Processing image.jpg...
• If an image fails, log the error and continue with the next one.
• Sort input files alphabetically for consistent numbering.
• After processing, offer to move originals to a _unprocessed/ subfolder inside the source directory.

Script Template

Use this as a base when generating the processing script:

#!/bin/bash
set -euo pipefail

SOURCE_DIR="<source>"
OUTPUT_DIR="<source>-optimized"
PREFIX="<prefix>"

mkdir -p "$OUTPUT_DIR"

counter=<start_number>
total_original=0
total_final=0
errors=0

files=()
while IFS= read -r -d '' f; do
    files+=("$f")
done < <(find "$SOURCE_DIR" -maxdepth 1 -type f \( -iname "*.jpg" -o -iname "*.jpeg" -o -iname "*.png" -o -iname "*.heic" -o -iname "*.heif" -o -iname "*.tiff" -o -iname "*.webp" -o -iname "*.bmp" \) -print0 | sort -z)

TOTAL=${#files[@]}
echo "Processing $TOTAL images..."

for img in "${files[@]}"; do
    basename_img=$(basename "$img")
    new_name="${PREFIX}-${counter}.jpg"
    output_path="$OUTPUT_DIR/$new_name"

    original_size=$(stat -f%z "$img")
    original_kb=$((original_size / 1024))
    total_original=$((total_original + original_kb))

    dims=$(magick identify -format "%wx%h" "$img" 2>/dev/null || echo "0x0")
    width="${dims%%x*}"
    height="${dims##*x}"

    if [ "$width" -gt "$height" ]; then
        resize_opt="-resize 1250x"
    else
        resize_opt="-resize x1250"
    fi

    quality=82
    if ! magick "$img" -auto-orient -strip $resize_opt -quality $quality \
        -sampling-factor 4:2:0 -colorspace sRGB "$output_path" 2>/dev/null; then
        printf "[%2d/%d] %-45s  ERRO\n" "$counter" "$TOTAL" "$basename_img"
        errors=$((errors + 1))
        counter=$((counter + 1))
        continue
    fi

    current_kb=$(( $(stat -f%z "$output_path") / 1024 ))

    while [ "$current_kb" -gt 400 ] && [ "$quality" -gt 50 ]; do
        quality=$((quality - 5))
        magick "$img" -auto-orient -strip $resize_opt -quality $quality \
            -sampling-factor 4:2:0 -colorspace sRGB "$output_path" 2>/dev/null
        current_kb=$(( $(stat -f%z "$output_path") / 1024 ))
    done

    total_final=$((total_final + current_kb))
    reduction=$(( (original_kb - current_kb) * 100 / original_kb ))
    final_dims=$(magick identify -format "%wx%h" "$output_path" 2>/dev/null)

    printf "[%2d/%d] %-45s %5dKB -> %-40s %4dKB (q%d, %s, -%d%%)\n" \
        "$counter" "$TOTAL" "$basename_img" "$original_kb" "$new_name" \
        "$current_kb" "$quality" "$final_dims" "$reduction"

    counter=$((counter + 1))
done

echo ""
echo "=== RESUMO ==="
echo "Processadas: $((counter - 1 - errors)) / $TOTAL"
[ "$errors" -gt 0 ] && echo "Erros: $errors"
echo "Antes:  $((total_original / 1024)) MB"
echo "Depois: $((total_final / 1024)) MB"
echo "Reducao: $(( (total_original - total_final) * 100 / total_original ))%"