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sail(1)

SAIL(1) SAIL command-line utility SAIL(1)

NAME

sail - SAIL command-line utility for image conversion

SYNOPSIS

sail [OPTIONS] COMMAND [ARGUMENTS]

DESCRIPTION

SAIL (Simple Abstract Imaging Library) is a cross-platform imaging library that provides a unified API for loading, saving, and manipulating images in various formats.

GLOBAL OPTIONS

-h, --help
Display help message and exit.
-v, --version
Display version information and exit.
-l, --log-level LEVEL
Set log level. Valid levels are:
  • silence - No output
  • error - Error messages only
  • warning - Warnings and errors (default)
  • info - Informational messages
  • message - All messages
  • debug - Debug information
  • trace - Detailed trace information

COMMANDS

list

List all supported image codecs with details.

Usage:

sail list [-v]

-v
Verbose output with detailed codec information.

convert

Convert, compose, and extract image files.

Usage:

sail convert [OPTIONS] INPUT... OUTPUT

-p, --pixel-format FORMAT
Force specific output pixel format. Common formats include:
  • BPP24-RGB - 24-bit RGB
  • BPP32-RGBA - 32-bit RGBA
  • BPP8-GRAYSCALE - 8-bit grayscale
  • BPP8-INDEXED - 8-bit indexed color

-c, --compression LEVEL
Set compression quality level (codec-specific). Use -1 for default compression.

-m, --max-frames COUNT
Limit number of frames to process. Use 0 to process all frames.

-n, --frame-number N
Extract specific frame number N (1-based). This is useful for extracting a single frame from animated images.

-d, --delay MS
Set frame delay for animations in milliseconds.

-e, --extract-frames
Extract each frame to separate file. Output filename will be in the format BASE-N.EXT where N is the frame number.

-C, --colors N
Quantize image to N colors (2-256) using Wu algorithm. This reduces the number of colors in the image for smaller file sizes.

-D, --dither
Apply Floyd-Steinberg dithering for better gradients when reducing colors.

-b, --background COLOR
Blend alpha channel with background color. Valid colors are:
  • white - White background
  • black - Black background
  • #RRGGBB - Hex color code (e.g., #FF0000 for red)

-s, --strip
Remove all metadata from output files.

-H, --flip-horizontal
Flip image horizontally (mirror left-right).

-V, --flip-vertical
Flip image vertically (mirror top-bottom).

probe

Display detailed information about image file.

Usage:

sail probe PATH

decode

Decode file and show information for all frames.

Usage:

sail decode PATH

EXAMPLES

Basic conversion:

# Convert JPEG to PNG:

sail convert input.jpg output.png

# Convert with custom quality:

sail convert input.png output.jpg -c 90 -p BPP24-RGB

Animation handling:

# Convert animation with specified frame delay:

sail convert animation.gif output.webp -d 100

# Convert animation to multi-page document:

sail convert animation.gif output.tiff

# Compose multiple images into single animation:

sail convert frame1.png frame2.png frame3.png animation.gif -d 100

Frame extraction:

# Extract all frames from animation:

sail convert animation.gif frame.jpg -e

# Extract first 5 frames only:

sail convert animation.webp frame.png -e -m 5

# Extract specific frame (e.g., frame 2):

sail convert animation.gif frame2.png -n 2

Color reduction:

# Reduce colors to 16 with dithering:

sail convert photo.jpg output.gif --colors 16 --dither

Alpha channel handling:

# Convert RGBA to RGB with white background:

sail convert transparent.png opaque.jpg --background white

Metadata and transformations:

# Strip metadata for privacy:

sail convert photo.jpg clean.jpg --strip

# Flip image horizontally and vertically:

sail convert photo.jpg flipped.jpg -H -V

Information display:

# Show detailed image information:

sail probe image.png

# Decode and show all frame information:

sail decode animation.gif

# List all supported codecs:

sail list -v

SUPPORTED FORMATS

SAIL supports a wide range of image formats including:

AVIF, BMP, GIF, HEIF, ICO, JPEG, JPEG2000, PNG, TIFF, and other.

Use sail list to see all supported formats and their capabilities.

EXIT STATUS

sail returns 0 on success, or a SAIL error code on failure. Common error codes include:

0
Success
3
SAIL_ERROR_OPEN_FILE - Failed to open file (file not found, permission denied, etc.)
9
SAIL_ERROR_INVALID_ARGUMENT - Invalid command line arguments
51
SAIL_ERROR_INVALID_IMAGE - Invalid or corrupted image file

For a complete list of SAIL error codes, see the SAIL library documentation.

SEE ALSO

For more information about SAIL, visit: https://sail.software

AUTHOR

SAIL was written by Dzmitry Baryshau and contributors.

COPYRIGHT

Copyright (c) 2020-2025 Dzmitry Baryshau. Licensed under the MIT License.

October 2025 SAIL 0.9.10