WebP file format plug-in for Photoshop

Current plug-in version: WebPShop 0.4.3

WebPShop is a Photoshop module for opening and saving WebP images, including animations.

Important note: Photoshop 23.2 and newer natively supports WebP. However some features such as preview at encoding and animations are missing. WebPShop can still be installed and used for these use cases and/or for Photoshop 23.1 and below.

Please look at the files LICENSE and CONTRIBUTING in the "docs" folder before using the contents of this repository or contributing.

Installation

Download the binary at https://github.com/webmproject/WebPShop/releases.
Direct link for Windows x64: https://github.com/webmproject/WebPShop/releases/download/v0.4.3/WebPShop_0_4_3_Win_x64.8bi
Direct link for MacOS (extract the ZIP archive afterwise): https://github.com/webmproject/WebPShop/releases/download/v0.4.2/WebPShop_0_4_2_Mac_Universal.zip
Move the plug-in (the .8bi binary for Windows or the .plugin folder for MacOS) to the Photoshop plug-in directory (C:\Program Files\Common Files\Adobe\Plug-Ins\CC for Windows, /Library/Application Support/Adobe/Plug-Ins/CC for Mac). Run Photoshop.

On macOS 10.15+, the prompt "WebPShop.plugin cannot be opened because the developer cannot be verified" can be bypassed by running the following in Terminal (Finder > Applications > Utilities):

sudo xattr -r -d com.apple.quarantine /Library/Application\ Support/Adobe/Plug-Ins/CC/WebPShop.plugin

Features

Open, Open As menu commands can be used to read .webp files.
Save a Copy... menu command can be used to write .webp files. Encoding parameters can be tuned through the UI.

Photoshop 23.2 and above has partial native WebP support. It will appear as WebP (*.WEBP) in the "Save as type:" drop-down list at encoding. WebPShop will still appear as WebPShop (*.WEBP, *.WEBP). Use the latter.
WebPShop can also be used at decoding through the "Open as..." menu.

Encoding settings

For information, the quality slider maps the following ranges to their internal WebP counterparts (see SetWebPConfig() in WebPShopEncodeUtils.cpp):

| Quality slider value   -> | 0    ...    97 | 98         99 |    100   |
|---------------------------|----------------|---------------|----------|
| WebP encoding settings -> | Lossy, quality | Near-lossless | Lossless |
|                           | 0    ...   100 | 60         80 |          |

The radio buttons offer several levels of compression effort:

| Label   | WebP speed setting  | Sharp YUV    | WebP "quality" setting |
|         |                     | (lossy only) | (except for lossy)     |
|---------|---------------------|--------------|------------------------|
| Fastest |          1          |      No      |            0           |
| Default |          4          |      No      |           75           |
| Slowest |          6          |      Yes     |          100           |

Animations are supported through a specific layer naming pattern:

FrameX (123 ms) (last frame in chronological order)
...
Frame3 (1111 ms) (third frame, shown for 1.111 seconds)
Frame2 (321 ms) (second frame, shown for 0.321 seconds)
Frame1 (2000 ms) (first frame, shown during the first two seconds of the animation)

All layers must be rasterized, of the same dimensions, and have no filter, mask, group, link, etc. Please see the detailed guidelines.

Limitations

Only English is currently supported.
Only "RGB Color" image mode is currently supported.
16 and 32 bits/channels are downscaled to 8 bits/channels before the WebP encoding because WebP only supports 8-bit internally. Exports from 32-bit documents should include the color profile in the WebP encoding settings, otherwise they might appear darker than expected.
WebP images cannot exceed 16383 x 16383 pixels.
The Timeline data is not used; thus animations rely on layers for defining frames (set duration as "(123 ms)" in each layer's name), and they need to be rasterized before saving.
On some images, lossless compression might produce smaller file sizes than lossy. That's why the quality slider is not linear. The same problem exists with the radio buttons controlling the compression effort.
The color profile is not applied to the Preview image on macOS, regardless of the related checkbox state.
This plug-in does not extend Export As neither Save for Web.
Encoding and decoding are done in a single pass. It is not currently possible to cancel such actions, and it might take some time on big images.
Only the latest Photoshop release is supported.

Troubleshooting

If the plug-in is not detected or does not behave as expected, the steps below might help:

Update Photoshop to the latest version.
Double-check that the plug-in binaries match the Operating System and the architecture.
The plug-in should be listed in the "Help > About Plugins" submenu if it is found by Photoshop.
If it is undetected, disable any antivirus program or allow the plug-in execution (including in MacOS and Windows built-in protections).

If it is still undetected, try each of these folders. Windows paths:

C:\Program Files\Common Files\Adobe\Plug-Ins\CC
C:\Program Files\Common Files\Adobe\Plug-Ins\CC\File Formats
C:\Program Files\Adobe\Adobe Photoshop 2022\Plug-ins

MacOS paths:

/Library/Application Support/Adobe/Plug-Ins/CC
Applications/Adobe Photoshop/Plug-ins/

If it is still undetected, remove all plug-ins from all folders and copy WebPShop in only one of these folders, in case there is a plug-in conflict. Restart the computer and/or Photoshop.

If the issue still occurs, check https://github.com/webmproject/WebPShop/issues to see if it is already mentioned or open a new bug report otherwise.

Software architecture

The common folder contains the following:

WebPShop.h is the main header, containing most functions.
WebPShop.cpp contains the plug-in entry point (called by host).
WebPShop.r and WebPShopTerminology.h represent the plug-in properties.
Functions in WebPShopSelector* are called in WebPShop.cpp.
WebPShop*Utils.cpp are helper functions.
WebPShopScripting.cpp is mostly used for automation.
WebPShopUI* display the encoding parameters window and the About box.

The win folder contains a Visual Studio solution and project, alongside with WebPShop.rc which is the encoding parameters window layout and About box.

The mac folder contains an XCode project. WebPShopUIDialog_mac.h and .mm describe the UI layout, while WebPShopUI_mac.mm handles the window events.

Build

Current libwebp version: WebP 1.2.2

Use Microsoft Visual Studio (2019 and above) for Windows and XCode for Mac.

Download the latest Adobe Photoshop Plug-In and Connection SDK at https://console.adobe.io/downloads/ps,
Put the contents of this repository in a "webpshop" folder located at adobe_photoshop_sdk_[version]/pluginsdk/samplecode/format,
Download the latest WebP binaries at https://developers.google.com/speed/webp/docs/precompiled or build them,
Add path/to/webp/includes and path/to/webp/includes/src as Additional Include Directories to the WebPShop project [1],
Add webp, webpdemux, webpmux libraries as Additional Dependencies to the WebPShop project [1],
Build with the same architecture and configuration as your Photoshop installation and the WebP binaries (x64 or arm64, Debug/Release),
By example for Windows, it should output the plug-in file WebPShop.8bi in adobe_photoshop_sdk_[version]/pluginsdk/samplecode/Output/Win/x64/Release.

[1] By default the XCode project includes and links to the libwebp-[version]-mac-[version] folder in the webpshop directory. The VS project expects libwebp-[version]-windows-x64 (or -arm64).