Image

Image formats

ALTO Image recognizes a stable set of image formats, but recognition does not mean that the installed driver can decode or encode every one. Check the four distinct capabilities before choosing a workflow:

  • Known means Format represents the format and its common extensions and media type.
  • Detectable means ALTO can identify and inspect a supported source header.
  • Readable means the selected GD or Imagick build can decode its pixels.
  • Writable means that build can encode a requested output.

Run the deployment's capability check for the authoritative read and write lists:

$ vendor/bin/image doctor

Supported formats

Format Common input names Alpha Animation Notes
JPEG .jpg, .jpeg, .jpe, .jfif No No Widely readable and writable; quality is lossy.
PNG .png Yes No Lossless output; metadata support depends on the driver.
WebP .webp Yes Yes Build-dependent read and write support; only the first input frame is used.
AVIF .avif, .avifs Yes Yes Requires a matching GD build or ImageMagick delegate.
JPEG XL .jxl Yes Yes Known by ALTO; current driver support depends on installed delegates.
HEIC .heic, .heif, .hif Yes Yes Imagick only when its ImageMagick build has a HEIC delegate.
TIFF .tif, .tiff Yes No Imagick support depends on its ImageMagick delegates.
GIF .gif Yes Yes GD and Imagick use the first input frame.
BMP .bmp, .dib No No GD support depends on its build; Imagick depends on delegates.
SVG .svg, .svgz Yes No Vector source; Imagick rasterizes it at its declared size. GD refuses it.

Animation in the table describes the file format, not multi-frame processing by this package. ALTO Image currently renders the first frame and reports that approximation. SVG can be detected and planned without implying that a raster driver is available.

Select a format

Format::of() accepts a format name, extension, or media type. It normalizes aliases such as jpg, .tiff, and image/svg+xml:

<?php

use Alto\Image\Format;

$format = Format::of('image/webp');

echo $format->extension(); // webp
echo $format->mime();      // image/webp

The enum also exposes supportsAlpha(), supportsAnimation(), isVector(), isLossy(), and a format-specific defaultQuality().

Check the active driver

Driver capabilities are discovered at runtime. Capabilities::$reads and Capabilities::$writes contain the exact Format cases available in that installed build. A filename extension alone does not prove read or write support.

Use Drivers to compare GD and Imagick.

Encode output

Encoding selects the output format and its compression settings.

Named formats

Use a named method for common settings:

<?php

use Alto\Image\Effort;
use Alto\Image\Image;

$image = Image::open('photo.png')
    ->fit(1600, 1600)
    ->webp(quality: 82, effort: Effort::Best);

Available methods are jpeg(), png(), webp(), and avif().

Full configuration

Use encode() for byte limits, progressive JPEG, or lossless output:

<?php

use Alto\Image\Format;
use Alto\Image\Image;

$image = Image::open('photo.png')->encode(
    format: Format::Webp,
    quality: 82,
    maxBytes: 200_000,
);

A byte limit can require several encoding passes. Use encode() with another Format case when the selected driver reports it as writable through vendor/bin/image doctor.

The complete encoding request includes the format, quality, effort, metadata policy, byte limit, progressive mode, lossless mode, and driver-specific options. The request remains immutable when one of these settings changes.