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Netpbm Windows Imaging Component Codec

Build and test

This Windows Imaging Component (WIC) codec makes it possible to decode .pgm and .ppm files with Windows applications that can leverage WIC codecs. It makes it possible to view Netpbm encoded images in Windows PhotoViewer, Windows Explorer (including thumbnails) and import these images in Microsoft Office documents.

It is a C++ 23 implementation originally based on the PNM WIC Image Codec project. It leverages the C++/WinRT framework to implement the classic COM components required for a WIC codec and uses Wix v5 for the installer.

Introduction

Netpbm is the name of an open source package of graphics programs and a programming library. It defines several graphics formats that are not compressed but are easy to exchange between different platforms:

Type Extension Magic number Color model
Portable BitMap .pbm P1,P4 0-1 (white & black)
Portable GrayMap .pgm P2,P5 0-255, 0-65535 * 1 channel (gray scale)
Portable Pixel Map .ppm P3,P6 0-255, 0-65535 * 3 channels (RGB)
Portable AnyMap .pnm P1,P2,P3,P4,P5,P6 Several
Portable Arbitrary Map .pam P7 Several

Color Model \ Color Space

The Netpbm format only supports to store the color model but not the actual color space. Several color spaces are used in practice, for example: BT.709 and sRGB. As no color space information is available the codec doesn't provide it through its COM interface. It is up to to displaying application to select the matching color space. For RGB images this is typical sRGB on Windows.

WIC

The Windows Imaging Component (WIC) is a built-in codec framework of Windows that makes it possible to create independent native image codecs that can be used by a large set of applications. WIC is implemented using COM technology. Image codecs for many popular formats are already pre-installed on Windows.

Installing

Requirements

  • Windows 11 or Windows 10 (version 22H2).
  • x86, x64 or ARM64 processor

Via GitHub with EXE

Go to the releases page and click on Assets at the bottom to show the files available in the release. Please use the appropriate installer that matches your machine's architecture.

Note

Microsoft Defender SmartScreen may show a warning about an unrecognised app when running the installer. Click on "More Info" + "Run anyway" to continue the installation.
The installer and the DLL are signed, but Defender SmartScreen requires an EV code signing certificate, which is only available to commercial organisations.

Applications that can use the Netpbm WIC codec

The following application have been validated to work with the Netpbm WIC codec:

  • Windows Explorer Thumbnail cache. This functionality allows Windows Explorer to show previews of images.
  • Windows Photo Viewer.
    Note: On clean installations of Windows 10 this component is installed but not registered. An registry file called restore-windows-photo-viewer.reg is provided to restore this functionality. The standard Windows Registry Editor can be used to add import this .reg file.
  • WIC Explorer (sample application from Microsoft). An updated version of this application can be found at https://github.com/vbaderks/WICExplorer
  • ZackViewer https://github.com/peirick/ZackViewer. This viewer can also be used to convert from one image encoding format to another.
  • Microsoft Office applications like Word, Excel, PowerPoint. These applications can, when the NetPbm codec is installed, import .pgm images in their documents. The 32 bit version of Office requires that the x86 version of the codec is installed.

Windows 11\10 Microsoft Photos Application not supported

The standard Windows 11\10 Microsoft Photos application cannot be used at this moment as it is limited to the WIC codecs that are pre-installed on Windows or are provided by Microsoft in the Microsoft Store. Microsoft currently does not make it possible to create WIC codecs that can be uploaded to the Microsoft Store.

WIC Codec Identity

The following table provides the codec identification information:

Property
Formal Name Netpbm Format
File Name Extension .pgm, .ppm
MIME type image/x-pgm

The following table lists the GUIDs used to identify the native Netpbm codec components:

Component GUID
Container Format 70ab66f5-cd48-43a1-aa29-10131b7f4ff1
Decoder Class ID 06891bbe-cc02-4bb2-9cf0-303fc4e668c3

The following table lists the formats that can be decoded:

Magic Component Count Bits per Sample WIC Pixel Format GUID
P5 1 2 GUID_WICPixelFormat2bppGray
P5 1 4 GUID_WICPixelFormat4bppGray
P5 1 8 GUID_WICPixelFormat8bppGray
P5 1 10,12,16* GUID_WICPixelFormat16bppGray
P6 3 8 GUID_WICPixelFormat24bppRGB
P6 3 16 GUID_WICPixelFormat48bppRGB

Note *: monochrome images with 10 or 12 bits per sample will be upscaled to 16 bits per sample.

Manual Build Instructions

  1. Clone this repro
  2. Use Visual Studio 2022 17.11 or newer and open the netpbm-wic-codec.sln. Batch build all projects.
  3. Or use a Developer Command Prompt and run use MSBuild in the root of the cloned repository.

Installation

  1. Open a command prompt with elevated rights
  2. Navigate to folder with the netpbm-wic-codec.dll
  3. Execute:
regsvr32 netpbm-wic-codec.dll

Uninstall

  1. Open a command prompt with elevated rights
  2. Navigate to folder with the netpbm-wic-codec.dll
  3. Execute:
regsvr32 -u netpbm-wic-codec.dll

Building and code signing

A command file is available to build and sign the WIC DLL and the setup application.
Instructions:

  • Open a Visual Studio Developer Command Prompt
  • Go the root of the cloned repository
  • Ensure a code signing certificate is available
  • Execute the command create-signed-builds.cmd certificate-thumb-print time-stamp-url
    Note: the certificate thumbprint and time stamp URL arguments are depending on the used code signing certificate.

The WIC DLL and the installer will be signed for the release builds of x86, x64 and ARM64.