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https://github.com/google/guetzli

Perceptual JPEG encoder
https://github.com/google/guetzli

jpeg-encoder

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Perceptual JPEG encoder

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README 

        
Guetzli



# Introduction



Guetzli is a JPEG encoder that aims for excellent compression density at high

visual quality. Guetzli-generated images are typically 20-30% smaller than

images of equivalent quality generated by libjpeg. Guetzli generates only

sequential (nonprogressive) JPEGs due to faster decompression speeds they offer.



[![Build Status](https://travis-ci.org/google/guetzli.svg?branch=master)](https://travis-ci.org/google/guetzli)



# Building



## On POSIX systems



1.  Get a copy of the source code, either by cloning this repository, or by

    downloading an

    [archive](https://github.com/google/guetzli/archive/master.zip) and

    unpacking it.

2.  Install [libpng](http://www.libpng.org/pub/png/libpng.html).

    If using your operating system

    package manager, install development versions of the packages if the

    distinction exists.

    *   On Ubuntu, do `apt-get install libpng-dev`.

    *   On Fedora, do `dnf install libpng-devel`. 

    *   On Arch Linux, do `pacman -S libpng`.

    *   On Alpine Linux, do `apk add libpng-dev`.

3.  Run `make` and expect the binary to be created in `bin/Release/guetzli`.



## On Windows



1.  Get a copy of the source code, either by cloning this repository, or by

    downloading an

    [archive](https://github.com/google/guetzli/archive/master.zip) and

    unpacking it.

2.  Install [Visual Studio 2015](https://www.visualstudio.com) and

    [vcpkg](https://github.com/Microsoft/vcpkg)

3.  Install `libpng` using vcpkg: `.\vcpkg install libpng`.

4.  Cause the installed packages to be available system-wide: `.\vcpkg integrate

    install`. If you prefer not to do this, refer to [vcpkg's

    documentation](https://github.com/Microsoft/vcpkg/blob/master/docs/EXAMPLES.md#example-1-2).

5.  Open the Visual Studio project enclosed in the repository and build it.



## On macOS



To install using [Homebrew](https://brew.sh/):

1. Install [Homebrew](https://brew.sh/)

2. `brew install guetzli`



To install using the repository:

1.  Get a copy of the source code, either by cloning this repository, or by

    downloading an

    [archive](https://github.com/google/guetzli/archive/master.zip) and

    unpacking it.

2.  Install [Homebrew](https://brew.sh/) or [MacPorts](https://www.macports.org/)

3.  Install `libpng`

    *   Using [Homebrew](https://brew.sh/): `brew install libpng`.

    *   Using [MacPorts](https://www.macports.org/): `port install libpng` (You may need to use `sudo`).

4.  Run the following command to build the binary in `bin/Release/guetzli`.

    *   If you installed using [Homebrew](https://brew.sh/) simply use `make`

    *   If you installed using [MacPorts](https://www.macports.org/) use `CFLAGS='-I/opt/local/include' LDFLAGS='-L/opt/local/lib' make`



## With Bazel



There's also a [Bazel](https://bazel.build) build configuration provided. If you

have Bazel installed, you can also compile Guetzli by running `bazel build -c opt //:guetzli`.



# Using



**Note:** Guetzli uses a large amount of memory. You should provide 300MB of

memory per 1MPix of the input image.



**Note:** Guetzli uses a significant amount of CPU time. You should count on

using about 1 minute of CPU per 1 MPix of input image.



**Note:** Guetzli assumes that input is in **sRGB profile** with a **gamma of

2.2**. Guetzli will ignore any color-profile metadata in the image.



To try out Guetzli you need to [build](#building) or

[download](https://github.com/google/guetzli/releases) the Guetzli binary. The

binary reads a PNG or JPEG image and creates an optimized JPEG image:



```bash

guetzli [--quality Q] [--verbose] original.png output.jpg

guetzli [--quality Q] [--verbose] original.jpg output.jpg

```



Note that Guetzli is designed to work on high quality images. You should always

prefer providing uncompressed input images (e.g. that haven't been already

compressed with any JPEG encoders, including Guetzli). While it will work on other

images too, results will be poorer. You can try compressing an enclosed [sample

high quality

image](https://github.com/google/guetzli/releases/download/v0/bees.png).



You can pass a `--quality Q` parameter to set quality in units equivalent to

libjpeg quality. You can also pass a `--verbose` flag to see a trace of encoding

attempts made.



Please note that JPEG images do not support alpha channel (transparency). If the

input is a PNG with an alpha channel, it will be overlaid on black background

before encoding.