HEIF(3)

NAME
Imager::File::HEIF - read and write HEIF files

SYNOPSIS
  use Imager;
  # before Imager 1.013 you need to explicitly load this
  use Imager::File::HEIF;

  my $img = Imager->new;
  $img->read(file => "foo.heif")
    or die $img->errstr;

  # type won't be necessary if the extension is heif from Imager 1.008
  $img->write(file => "foo.heif", type => "heif")
    or die $img->errstr;

DESCRIPTION
Implements .heif file support for Imager.

CLASS METHODS

libversion()
buildversion()
      my $lib_version   = Imager::File::HEIF->libversion;
      my $build_version = Imager::File::HEIF->buildversion;

    Returns the version of "libheif", either the version of the library currently being used, or the version that Imager::File::HEIF was built with.

    These might differ because the library was updated after Imager::File::HEIF was built.

init()
deinit()
      Imager::File::HEIF->init;
      Imager::File::HEIF->deinit;

    You do not need to call these in normal code.

    Initialise or clean up respectively the state of "libheif".

    These require "libheif" 1.13.0 or later to have any effect.

    Imager::File::HEIF will call these on load and at "END" time respectively.

    In practice "libx265" still leaves a lot of memory leaked in my testing.

dump_encoders
      Imager::File::HEIF->dump_encoders

    Dump information about each encoder configured for "libheif" to standard output. See the "/encoders" method for programmatic access.

    For example:

      265 HEVC encoder (4.1+1-1d117be) (x265):
        Format: hevc
        Lossless: Yes
        Lossy: Yes
        Parameters:
          quality (int): 0 ... 100 (default 50)
          lossless (boolean): (default false)
          preset (str): "ultrafast" "superfast" "veryfast" "faster" "fast" "medium" "slow" "slower" "veryslow" "placebo" (default "slow")
          tune (str): "psnr" "ssim" "grain" "fastdecode" (default "ssim")
          tu-intra-depth (int): 1 ... 4 (default 2)
          complexity (int): 0 ... 100 (default 0)
          chroma (str): "420" "422" "444" (default "420")

    The first line for each is a descriptive name of the encoder followed by the identifier for that encoder, which can be supplied as "heif_encoder" when writing an image.

    "Format" is the compression supported by this encoder.

    "Lossless" reports whether the encoder supports lossless encoding.

    "Lossy" reports whether the encoder supports lossy encoding.

    "Parameters" lists the paremeters supported by this encoder, which can be set when writing.

dump_decoders
      Imager::File::HEIF->dump_decoders

    Dump information about each encoder. This provides very little information and may list a decoder more than once if it supports more than one (de-)compression.

      libde265 HEVC decoder, version 1.0.15 (libde265):
        Format: hevc
      FFMPEG HEVC decoder 7.1.3-0+deb13u1 (ffmpeg):
        Format: hevc
      libjpeg-turbo 2.1.5 (libjpeg 6.2) (jpeg):
        Format: jpeg

have_decoder_for($compression)
      if (Imager::File::HEIF->have_decoder_for("jpeg")) {
        ...

    Returns true if "libheif" supports decoding the given compression type. Throws an exception for a compression type that this version of "libheif" doesn't support.

have_encoder_for($compression)
      if (Imager::File::HEIF->have_encoder_for("jpeg")) {
        ...

    Returns true if "libheif" supports encoding the given compression type. Throws an exception for a compression type that this version of "libheif" doesn't support.

compression_names
    Returns a list of compression names suitable for the have_encoder_for, have_decoder_for and encoders methods, or for the "heif_compression" write parameter.

    This includes the "undefined" (not the perl "undef") method only accepted by the "encoders" method.

encoders
encoders($compression)
    Returns a list of Imager::File::HEIF::Encoder objects, which provides information about each encoder the "libheif" Imager::File::HEIF was built against.

    If $compression is supplied only decoders supporting that compression are returned. This defaults to "undefined" (not the perl "undef") which returns all encoders.

    If an unknown compression name is supplied this method will throw an exception.

PATENTS
The h.265 compression libheif uses is covered by patents, if you use this code for commercial purposes you may need to license those patents.

LICENSING
Imager::File::HEIF itself and Imager are licensed under the same terms as Perl itself, and "libheif" is licensed under the LGPL 3.0.

But "libx264", which "libheif" is typically built to use for encoding, is licensed under the GPL 2.0, and the owners provide a fairly strict interpretation of that license <https://www.x265.org/x265-licensing-faq/>. They also sell commercial licenses.

INSTALLATION
To install Imager::File::HEIF you need Imager installed and you need "libheif", "libde265" and "libx265" and their development files.

Imager::File::HEIF requires at least version 1.11.0 of "libheif", but in general you want the very latest version you can get. Imager::File::HEIF has been tested up to version 1.21.2 of "libheif".

1.14 through 1.16 need "LIBDE265" support installed as part of the library, not as a plugin.

STANDARD IMAGER TAGS
Imager::File::HEIF supports the "i_xres" and "i_yres" tags, but only for setting or retrieving the pixel aspect ratio. As generally a photographic or movie format, HEIF doesn't support physical resolution, which is generally a print or scan mechanism.

"i_aspect_only" is ignored on writing, "i_xres" and "i_yres" are treated as an aspect ratio.

When you read a HEIF image "i_xres" and "i_yres" are set from the aspect ratio and "i_aspect_only" is set to 1.

CONTROLLING COMPRESSION
You can control output through a number of tags, (implicitly set on the images via write() or write_multi()):

•   "heif_lossless" - if non-zero the image is compressed in "lossless" mode. Note that in both lossy and lossless modes the image is converted from the RGB colorspace to the YCbCr colorspace, which will lose information. In lossless mode the "heif_quality" value is ignored and irrelevant. Default: set by the "libheif" encoder.

•   "heif_quality" - a value from 0 to 100 representing the quality of lossy compression. Default: set by the "libheif" encoder.

•   "heif_compression" - the compression type to use, this defaults to "hevc". The values supported depend on the version of "libheif" and how it was built. You can use different compression methods for different images in a multi-image file, but don't be too surprised if readers fail to read it.

    Using a compression other than "hevc" with the ".heif" extension may confuse other software.

    Be aware this chooses the compression inside the ISOBMFF file, selecting "jpeg" compression does not produce a JPEF/JFIF file.

•   "heif_encoder" - the identifier of the encoder to use, this also sets the compression to use, if you also supply "heif_compression" and it doesn't match the compression used by this encoder writing will fail. Default: an encoder is selected by "libheif" based on the compression selected.

Other parameters set by the encoder can also be set by setting a tag with that name with a "heif_" prefix. You can see a list of parameters for each encoder using the dump_encoders() method, or by calling the parameters() method on the encoder object returned by the encoders() method.

So you can set the "chroma" with the "heif_chroma" tag:

  $img->write(..., heif_chroma => "444")...

Parameter names can contain dashes and these are reflected in the tag names:

  # from the AOM AV1 encoder
  $img->write(..., "heif_alpha-quality" => 80) ...

If the encoder has "quality" or "lossless" parameters those are handled by their dedicated APIs, not via the general "parameter" API.

If setting such a parameter fails, writing will fail.

Unfortunately the only way to see if the parameter was recognized is to enable logging and examine the log.

WARNING: from my testing, using the rough measure done by Imager i_img_diff(), lossy at 80 quality turned out closer to the original image than lossless.

RESOURCE USAGE
HEIF processing is fairly resource intensive, and libheif uses multiple decoding threads by default when you read a HEIF image.

With "libheif" 1.13.0 or later you can set $Imager::File::HEIF::MaxThreads to the maximum number of threads to use. If this is negative or not defined the default is used, which is defined by "libheif".

BUGS
Imager::File::HEIF have_decoder_for() returns false for "av1" before libheif 1.13, neither Imager::File::HEIF nor the libheif tools were able to decode "av1" encoded files created by the libheif tool, even with "av1" support enabled in libheif.

TODO

•   10-bit/sample and 12-bit/sample images. Based on <https://github.com/strukturag/libheif/issues/40> this might not be supported completely yet.

•   reading metadata (any to read?)

•   writing metadata. We don't seem to have the animation metadata that webp does. (image sequences seems to have it)

•   reading sub-image data? we can probably skip thumbs (or provide an option to read the thumb rather than the main image), but are there other images to read? Depth images. Low priority.

•   writing sub-image data? thumbnails and depth images. Very low priority.

•   Everything else.

GLOSSARY

ISOBMFF
    ISO Base Media File Format - the container file format defined by ISO/IEC 14496-12 used by HEIF, AVIF, JPEG2000 and many non-image formats. See https://en.wikipedia.org/wiki/ISO_base_media_file_format.

AUTHOR
Tony Cook <tony@develop-help.com>

SEE ALSO
Imager, Imager::Files.

https://en.wikipedia.org/wiki/High_Efficiency_Image_File_Format

https://github.com/strukturag/libheif

https://github.com/strukturag/libde265 - x265 decoder

https://www.x265.org/ - x265 encoder