grayscale

Convert color images to grayscale (black and white), removing all color information while preserving luminance. Perfect for creating artistic effects, reducing file sizes, or preparing images for black and white printing.

Usage

Terminal

$ mediaproc image grayscale <input> [options]

Alternative spelling (UK):

$ mediaproc image greyscale <input> [options]

Basic Syntax

Terminal

$ mediaproc image grayscale photo.jpg

✓ Converted to grayscale

$ mediaproc image grayscale photo.jpg -o blackandwhite.jpg

$ mediaproc image greyscale photo.jpg

Options

Option	Alias	Type	Default	Description
`--output`	`-o`	`string`	`[input]-grayscale.[ext]`	Output file path
`--quality`	`-q`	`number`	`90`	Output quality (1-100)
`--dry-run`		`boolean`	`false`	Preview operation without saving
`--verbose`	`-v`	`boolean`	`false`	Show detailed processing information

Examples

1. Basic Grayscale Conversion

Terminal

$ mediaproc image grayscale photo.jpg

✓ Converted to grayscale

$ mediaproc image grayscale color-photo.jpg -o bw-photo.jpg

$ mediaproc image greyscale portrait.jpg

2. High Quality Conversion

Terminal

$ mediaproc image grayscale photo.jpg -q 100 -o print-bw.jpg

$ mediaproc image grayscale photo.jpg -q 85 -o web-bw.jpg

$ mediaproc image grayscale photo.jpg -q 75 -o small-bw.jpg

3. Portrait Photography

# Classic black and white portrait
mediaproc image grayscale portrait.jpg -o portrait-bw.jpg

# High-quality studio portrait
mediaproc image grayscale studio-shot.jpg -q 100 -o studio-bw.jpg

# Batch convert portrait session
for img in portraits/*.jpg; do
  mediaproc image grayscale "$img" -o "bw/$(basename "$img")"
done

4. Artistic Photography

# Street photography
mediaproc image grayscale street-photo.jpg -o street-bw.jpg

# Architectural photography
mediaproc image grayscale building.jpg -o architecture-bw.jpg

# Fine art photography
mediaproc image grayscale landscape.jpg -q 100 -o fine-art-bw.jpg

5. Document Processing

# Convert scanned documents
mediaproc image grayscale scan-color.jpg -o scan-bw.jpg

# Reduce file size for documents
mediaproc image grayscale document.jpg -q 80 -o document-bw.jpg

# Batch process documents
for doc in documents/*.jpg; do
  mediaproc image grayscale "$doc" -o "bw-docs/$(basename "$doc")"
done

# Instagram black and white
mediaproc image grayscale post.jpg -o instagram-bw.jpg

# Twitter header
mediaproc image grayscale header.jpg -q 90 -o twitter-header-bw.jpg

# Profile picture
mediaproc image grayscale profile.jpg -o profile-bw.jpg

7. Print Preparation

# Newspaper print
mediaproc image grayscale photo.jpg -q 85 -o newspaper.jpg

# Magazine print (high quality)
mediaproc image grayscale photo.jpg -q 100 -o magazine-print.jpg

# Poster print
mediaproc image grayscale design.jpg -q 95 -o poster-bw.jpg

8. Batch Processing

# Convert all JPGs in directory
for img in *.jpg; do
  mediaproc image grayscale "$img" -o "bw/$(basename "$img")"
done

# Convert with consistent quality
for img in photos/*.jpg; do
  mediaproc image grayscale "$img" -q 90 -o "grayscale/$(basename "$img")"
done

# Convert multiple formats
for img in *.{jpg,png,webp}; do
  [ -f "$img" ] && mediaproc image grayscale "$img" -o "bw/${img%.*}-bw.${img##*.}"
done

9. Web Optimization

# Web-friendly grayscale
mediaproc image grayscale photo.jpg -q 80 -o web-bw.jpg

# Thumbnail grayscale
mediaproc image grayscale photo.jpg -q 75 -o thumb-bw.jpg

# Hero image grayscale
mediaproc image grayscale hero.jpg -q 90 -o hero-bw.jpg

10. Preview Before Converting

# Preview conversion
mediaproc image grayscale photo.jpg --dry-run

# Detailed preview
mediaproc image grayscale photo.jpg --dry-run --verbose

# Check file details
mediaproc image grayscale large-image.jpg --dry-run --verbose

11. E-commerce Product Photos

# Product photo variant
mediaproc image grayscale product.jpg -o product-bw.jpg

# Batch convert product catalog
for img in products/*.jpg; do
  mediaproc image grayscale "$img" -q 90 -o "catalog-bw/$(basename "$img")"
done

# Create alternate product views
mediaproc image grayscale main-product.jpg -o alternate-view.jpg

12. Historical Photo Effects

# Vintage look (start with grayscale)
mediaproc image grayscale modern-photo.jpg -o vintage-base.jpg

# Old photo restoration base
mediaproc image grayscale faded-color.jpg -o restoration-base.jpg

# Archive preparation
mediaproc image grayscale historical.jpg -q 100 -o archive-bw.jpg

13. Logo and Brand Elements

# Logo black and white version
mediaproc image grayscale logo-color.png -o logo-bw.png

# Brand asset variant
mediaproc image grayscale brand-image.jpg -o brand-bw.jpg

# Icon grayscale version
mediaproc image grayscale icon-color.svg -o icon-bw.svg

14. Scientific and Medical Imaging

# X-ray style conversion
mediaproc image grayscale medical-image.jpg -q 100 -o xray-style.jpg

# Scientific documentation
mediaproc image grayscale specimen.jpg -q 100 -o scientific-doc.jpg

# Research image preparation
mediaproc image grayscale research-photo.jpg -o research-bw.jpg

15. Combining with Other Operations

# Grayscale then contrast adjustment
mediaproc image grayscale photo.jpg -o temp.jpg
mediaproc image linear temp.jpg -a 1.2 -o high-contrast-bw.jpg
rm temp.jpg

# Resize then convert to grayscale
mediaproc image resize photo.jpg -w 1920 -o temp.jpg
mediaproc image grayscale temp.jpg -o final-bw.jpg
rm temp.jpg

# Grayscale then sharpen
mediaproc image grayscale photo.jpg -o temp.jpg
mediaproc image sharpen temp.jpg -o sharp-bw.jpg
rm temp.jpg

Use Cases

1. Artistic Photography

Black and White Art: Classic photographic art style
Street Photography: Emphasize composition over color
Portrait Photography: Timeless, classic look
Fine Art Prints: Gallery-quality black and white
Documentary Photography: Professional documentary style

2. Print and Publishing

Newspaper Printing: Reduce costs with grayscale
Magazine Layouts: Artistic editorial choices
Book Publishing: Classic book photography
Brochures: Cost-effective printing option
Newsletters: Professional appearance

3. Web and Digital Media

File Size Reduction: Smaller files load faster
Bandwidth Optimization: Reduce data usage
Consistent Aesthetics: Unified look across images
Professional Websites: Sophisticated appearance
Blog Content: Artistic blog photography

Instagram Aesthetic: Consistent black and white theme
Profile Pictures: Professional, timeless look
Story Content: Dramatic effect
Post Themes: Cohesive visual identity
Brand Identity: Recognizable style

5. Document Processing

Scan Optimization: Reduce scanned document size
Archive Preparation: Standardize historical documents
PDF Creation: Smaller PDF file sizes
Fax Preparation: Optimize for fax transmission
OCR Preparation: Better text recognition

6. E-commerce

Product Variants: Show product in different styles
Catalog Consistency: Uniform product presentation
Size Reduction: Faster page load times
Print Catalogs: Cost-effective printing
Alternate Views: Additional product perspectives

7. Professional Services

Legal Documents: Professional document imaging
Medical Records: Standardized medical imaging
Real Estate: Professional property photos
Corporate Materials: Professional corporate imaging
Resume/CV Photos: Professional headshots

Technical Details

Grayscale Conversion Method

The command uses Sharp's grayscale() method with perceptual luminance weighting:

Grayscale = 0.299 × Red + 0.587 × Green + 0.114 × Blue

This formula accounts for human eye sensitivity to different colors:

Green (58.7%): Eyes most sensitive to green
Red (29.9%): Moderate sensitivity
Blue (11.4%): Least sensitive

Visual Example

RGB(255, 0, 0) → Grayscale(76)    # Red
RGB(0, 255, 0) → Grayscale(150)   # Green (brightest)
RGB(0, 0, 255) → Grayscale(29)    # Blue (darkest)
RGB(128, 128, 128) → Grayscale(128) # Gray (unchanged)

File Size Benefits

Typical File Size Reduction:

JPEG: 30-40% smaller (grayscale vs color)
PNG: 40-50% smaller (single channel vs RGB)
WebP: 35-45% smaller
Reason: Single channel (grayscale) vs three channels (RGB)

Example:

Color JPEG: 2.5 MB
Grayscale JPEG: 1.7 MB (32% reduction)

Color PNG: 4.0 MB
Grayscale PNG: 2.2 MB (45% reduction)

Color Space Details

Input: RGB or RGBA
Output: Single-channel grayscale
Alpha Channel: Preserved if present (becomes grayscale + alpha)
Color Profile: sRGB luminance conversion
Bit Depth: Maintains input bit depth

Performance Characteristics

Speed: Very fast (simple channel operation)
Memory: Efficient (reduces channel count)
Quality: No interpolation, direct calculation
CPU: Minimal processing per pixel
Format Support: All image formats

Quality Considerations

Quality Settings:

100: Lossless/maximum quality (large files)
90-95: High quality (recommended for print)
85-90: Good quality (recommended for web)
75-85: Balanced quality (smaller files)
60-75: Lower quality (smallest files)

Format Recommendations:

JPEG: Best for photographs (good compression)
PNG: Best for graphics/text (lossless)
WebP: Best for web (good compression + quality)

Common Patterns

Pattern 1: Simple Conversion

# Most common use case
mediaproc image grayscale photo.jpg

Pattern 2: High-Quality Print

# Maximum quality for printing
mediaproc image grayscale photo.jpg -q 100 -o print.jpg

Pattern 3: Web-Optimized

# Balanced quality for web
mediaproc image grayscale photo.jpg -q 85 -o web.jpg

Pattern 4: Batch Conversion

# Convert all images in folder
for img in *.jpg; do
  mediaproc image grayscale "$img" -o "bw/$(basename "$img")"
done

Pattern 5: File Size Reduction

# Reduce size with grayscale and quality
mediaproc image grayscale large.jpg -q 75 -o optimized.jpg

Troubleshooting

Issue: Image Already Looks Grayscale

Problem: Converting grayscale image again

Solutions:

# Check if image is already grayscale
mediaproc image metadata photo.jpg

# Look for: channels: 1 (grayscale) vs channels: 3 (color)

# Converting grayscale to grayscale is harmless but unnecessary
# Output will be identical to input

Issue: Unexpected Brightness

Problem: Grayscale version appears darker/lighter than expected

Solutions:

# This is normal - colors convert to different grayscale values
# Red: 76, Green: 150, Blue: 29

# Bright colors (green) → brighter grayscale
# Dark colors (blue) → darker grayscale

# Adjust brightness after conversion if needed
mediaproc image grayscale photo.jpg -o temp.jpg
mediaproc image linear temp.jpg -a 1.2 -o brighter-bw.jpg

Issue: File Size Not Reduced

Problem: Grayscale file is same size as color

Solutions:

# File size depends on format and quality
# JPEG: Compression matters more than channels

# Try lower quality for size reduction
mediaproc image grayscale photo.jpg -q 75 -o smaller.jpg

# Or use more efficient format
mediaproc image grayscale photo.jpg -o photo.webp

# PNG will show biggest size reduction
mediaproc image grayscale photo.png -o smaller.png

Issue: Quality Loss

Problem: Grayscale image appears degraded

Solutions:

# Increase quality setting
mediaproc image grayscale photo.jpg -q 100 -o high-quality.jpg

# Use lossless format
mediaproc image grayscale photo.jpg -o lossless.png

# Grayscale conversion itself is lossless
# Quality loss is from output format compression

Issue: Color Bleeding

Problem: Slight color tint visible in grayscale

Solutions:

# Ensure complete grayscale conversion
# Convert twice if needed (shouldn't be necessary)
mediaproc image grayscale photo.jpg -o temp.jpg
mediaproc image grayscale temp.jpg -o final.jpg

# Or save as PNG to avoid JPEG artifacts
mediaproc image grayscale photo.jpg -o clean.png

Issue: UK vs US Spelling

Problem: Not sure which spelling to use

Solutions:

# Both spellings work identically
mediaproc image grayscale photo.jpg  # US spelling
mediaproc image greyscale photo.jpg  # UK spelling

# Use whichever you prefer
# Output is identical

Best Practices

Choose Appropriate Quality
- Print: Use quality 95-100
- Web: Use quality 80-90
- Thumbnails: Use quality 70-80
- Archives: Use quality 100 with PNG
Consider Output Format
- JPEG: Best for photographs
- PNG: Best for graphics/text
- WebP: Best compression for web
- TIFF: Best for archival
Preserve Originals
- Keep color originals
- Create grayscale copies
- Use descriptive file names
- Organize in separate folders
Batch Processing Efficiency
- Process similar images together
- Use consistent quality settings
- Create organized output structure
- Test with one image first
File Size Management
- Lower quality for smaller files
- Use efficient formats (WebP)
- Balance quality vs size
- Consider use case requirements
Creative Workflow
- Convert to grayscale early
- Easier to see composition
- Adjust contrast after conversion
- Fine-tune brightness as needed
Professional Output
- Maximum quality for client delivery
- Consistent settings for series
- Document conversion parameters
- Maintain metadata when possible

Integration Examples

With Other Image Commands

# Auto-enhance then convert to grayscale
mediaproc image auto-enhance photo.jpg -o enhanced.jpg
mediaproc image grayscale enhanced.jpg -o final-bw.jpg

# Grayscale then increase contrast
mediaproc image grayscale photo.jpg -o temp.jpg
mediaproc image linear temp.jpg -a 1.3 -o high-contrast.jpg

# Resize then convert to grayscale
mediaproc image resize photo.jpg -w 1920 -h 1080 -o temp.jpg
mediaproc image grayscale temp.jpg -o final.jpg

# Grayscale then apply sepia
mediaproc image grayscale photo.jpg -o bw.jpg
mediaproc image sepia bw.jpg -o sepia-toned.jpg

In Scripts

#!/bin/bash
# Convert and organize photo series to black and white

input_dir="originals"
output_dir="grayscale"

mkdir -p "$output_dir"

for img in "$input_dir"/*.jpg; do
  filename=$(basename "$img" .jpg)

  echo "Converting: $filename"

  # Convert to grayscale
  mediaproc image grayscale "$img" -q 90 -o "$output_dir/${filename}-bw.jpg"

  # Also create thumbnail
  mediaproc image resize "$output_dir/${filename}-bw.jpg" -w 400 -h 400 --fit cover -o "$output_dir/thumbs/${filename}-thumb.jpg"
done

echo "Conversion complete!"

Creating Print-Ready Files

#!/bin/bash
# Prepare images for black and white printing

input="photo.jpg"
output_base="print-ready"

# 1. Convert to high-quality grayscale
mediaproc image grayscale "$input" -q 100 -o "${output_base}-bw.jpg"

# 2. Adjust for print (slightly lighter)
mediaproc image linear "${output_base}-bw.jpg" -a 1 -b 10 -o "${output_base}-adjusted.jpg"

# 3. Sharpen for print
mediaproc image sharpen "${output_base}-adjusted.jpg" -o "${output_base}-final.jpg"

echo "Print-ready file created: ${output_base}-final.jpg"