Size

Detect AVIF, GIF, HEIF, JPEG, JPEG XL, PNG and WebP image dimensions with minimal memory usage. Pure Ruby, no deps.

Usage

size = Size.of("photo.jpg")
size.width  #=> 1920
size.height #=> 1080
size.pixels #=> 2073600
size.class  #=> Size::JPEG

Accepts a file path, Pathname or any readable IO:

File.open("photo.png", "rb") { |io| Size.of(io) }

Pattern matching works since Size is a Data class:

case Size.of(path)
in Size::PNG[width:, height:]
  "PNG: #{width}x#{height}"
in Size::JPEG[width:, height:]
  "JPEG: #{width}x#{height}"
end

Supports AVIF, GIF, HEIF, JPEG, JPEG XL, PNG and WebP. Raises Size::FormatError for unrecognized or truncated formats.

Installation

gem install size

Or add to your Gemfile:

gem "size"

Alternatives

FastImage is the most popular choice. It fetches dimensions from URLs, covers many more formats (BMP, TIFF, ICO, PSD, SVG and others) and has years of production use behind it. Locally it reads through a Fiber-based pipeline in 256-byte chunks.

ImageSize has the broadest format coverage, with BMP, PSD, SWF, XPM and more. It reads in cached 4,096-byte chunks.

Size covers seven formats and works only with local files and I/O objects. It reads the minimum each format requires: 10 bytes for a GIF, 12 for a JPEG XL codestream, 24 for a PNG, 25–30 for WebP and a small number of box headers for AVIF, HEIF and JPEG XL containers. All three gems stream through JPEG markers, but FastImage begins with 256 bytes in memory, ImageSize with 4,096 and Size with 12.

For URL support or broad format coverage, use FastImage or ImageSize. For the smallest possible memory usage, use Size.