PhoenixKit.Storage.ImageProcessor (phoenix_kit v1.5.1)

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ImageMagick-based image processing module.

Handles image operations using ImageMagick command-line tools:

  • identify - Extract image metadata (dimensions, format)
  • convert/magick - Resize and format conversion

This replaces Vix with ImageMagick, which is more widely trusted and has better long-term support.

Summary

Functions

extract_dimensions(file_path)

Extract both width and height from an image file.

get_height(file_path)

Get the height of an image file using ImageMagick identify.

get_width(file_path)

Get the width of an image file using ImageMagick identify.

resize(input_path, output_path, width, height, opts \\ [])

Resize an image to fit within specified dimensions.

resize_and_crop_center(input_path, output_path, width, height, opts \\ [])

Resize and center-crop an image to exact dimensions.

Functions

extract_dimensions(file_path)

Extract both width and height from an image file.

Uses ImageMagick's identify command to extract image dimensions.

Returns:

  • {:ok, {width, height}} - Dimensions in pixels
  • {:error, reason} - If extraction fails

get_height(file_path)

Get the height of an image file using ImageMagick identify.

Returns the height in pixels or nil if extraction fails.

get_width(file_path)

Get the width of an image file using ImageMagick identify.

Returns the width in pixels or nil if extraction fails.

resize(input_path, output_path, width, height, opts \\ [])

Resize an image to fit within specified dimensions.

Maintains aspect ratio by scaling to fit within bounds. Optionally converts format based on output_format parameter.

Parameters:

  • input_path - Path to input image file
  • output_path - Path to save resized image
  • width - Target width (nil to use original)
  • height - Target height (nil to use original)
  • opts - Additional options
    • :quality - JPEG quality 1-100 (default: 85)
    • :format - Output format override (jpg, png, webp, etc)

Returns:

  • {:ok, output_path} - Success
  • {:error, reason} - If resize fails

resize_and_crop_center(input_path, output_path, width, height, opts \\ [])

Resize and center-crop an image to exact dimensions.

Zooms into the image to fill the target dimensions completely, then center-crops to extract the exact target size. No padding borders - the entire output is filled with the image content.

This is ideal for thumbnails where you want perfect squares (e.g., 150x150) with the image zoomed in and centered, no white/black borders.

The algorithm:

  1. Resizes image to fill the target box (scales to cover both dimensions)
  2. Centers the image using gravity
  3. Crops from center to exact target dimensions

Parameters:

  • input_path - Path to input image file
  • output_path - Path to save cropped image
  • width - Target width (required)
  • height - Target height (required)
  • opts - Additional options
    • :quality - JPEG quality 1-100 (default: 85)
    • :format - Output format override (jpg, png, webp, etc)
    • :background - Background color (rarely used, default: "white")

Returns:

  • {:ok, output_path} - Success
  • {:error, reason} - If processing fails