bindbc-freeimage 1.0.0

bindbc-freeimage

This project provides both static and dynamic bindings to the FreeImage library. They are @nogc and nothrow compatible and can be compiled for compatibility with -betterC. This package is intended as a replacement of DerelictFI, which is not compatible with @nogc, nothrow, or -betterC.

Usage

By default, bindbc-freeimage is configured to compile as a dynamic binding that is not -betterC compatible. The dynamic binding has no link-time dependency on the FreeImage library, so the FreeImage shared library must be manually loaded at run time. When configured as a static binding, there is a link-time dependency on the FreeImage library---either the static library or the appropriate file for linking with shared libraries on your platform (see below).

When using DUB to manage your project, the static binding can be enabled via a DUB subConfiguration statement in your project's package file. -betterC compatibility is also enabled via subconfigurations.

To use FreeImage, add bindbc-freeimage as a dependency to your project's package config file. For example, the following is configured to compile FreeImage as a dynamic binding that is not -betterC compatible:

dub.json

dependencies {
    "bindbc-freeimage": "~>1.0.0",
}

dub.sdl

dependency "bindbc-freeimage" version="~>1.0.0"

The dynamic binding

The dynamic binding requires no special configuration when using DUB to manage your project. There is no link-time dependency. At run time, the FreeImage shared library is required to be on the shared library search path of the user's system. On Windows, this is typically handled by distributing the FreeImage DLL with your program. On other systems, it usually means the user must install the FreeImage shared library through a package manager.

To load the shared library, you need to call the loadFreeImage function. This returns a member of the FISupport enumeration (see the README for bindbc.loader for the error handling API):

• FISupport.noLibrary indicating that the library failed to load (it couldn't be found)
• FISupport.badLibrary indicating that one or more symbols in the library failed to load
• a member of FISupport indicating a version number that matches the version of FreeImage that bindbc-freeimage was configured at compile-time to load. By default, that is FISupport.fi317, but can be configured via a version identifier (see below). This value will match the global manifest constant, fiSupport.

import bindbc.freeimage;

/*
This version attempts to load the FreeImage shared library using well-known variations
of the library name for the host system.
*/
FISupport ret = loadFreeImage();
if(ret != fiSupport) {

    // Handle error. For most use cases, its reasonable to use the the error handling API in
    // bindbc-loader to retrieve error messages for logging and then abort. If necessary, it's
    // possible to determine the root cause via the return value:

    if(ret == FISupport.noLibrary) {
        // FreeImage shared library failed to load
    }
    else if(FISupport.badLibrary) {
        // One or more symbols failed to load. The likely cause is that the
        // shared library is for a lower version than bindbc-freeimage was configured
        // to load.
    }
}

/*
This version attempts to load the FreeImage library using a user-supplied file name.
Usually, the name and/or path used will be platform specific, as in this example
which attempts to load `freeimage.dll` from the `libs` subdirectory, relative
to the executable, only on Windows.
*/
// version(Windows) loadFreeImage("libs/freeimage.dll")

By default, the bindbc-freeimage binding is configured to load FreeImage 3.17. This behavior can be overridden via the -version compiler switch or the versions DUB directive with the desired FreeImage version number. It is recommended that you always select the minimum version you require and no higher. In this next example, the FreeImage dynamic binding is compiled to support FreeImage 3.18:

dub.json

"dependencies": {
    "bindbc-freeimage": "~>1.0.0"
},
"versions": ["FI_318"]

dub.sdl

dependency "bindbc-freeimage" version="~>1.0.0"
versions "FI_318"

With this example configuration, fiSupport == FISupport.fi318 on a successful load. If FreeImage 3.18 or later is installed on the user's system, loadFreeImage will return FISupport.fi318. If FreeImage 3.17 is found instead, loadFreeImage will return FISupport.badLibrary. In this scenario, calling loadedFreeImageVersion() will return a FISupport member indicating which version of FreeImage, if any, actually loaded. If a lower version was loaded, it's still possible to call functions from that version of FreeImage, but any calls to functions from higher versions will result in a null pointer access. For this reason, it's recommended to always specify your required version of the FreeImage library at compile time and abort when you receive an FISupport.badLibrary return value from loadFreeImage.

No matter which version was configured, the successfully loaded version can be obtained via a call to loadedFreeImageVersion. It returns one of the following:

• FISupport.noLibrary if loadFreeImage returned FISupport.noLibrary
• FISupport.badLibrary if loadFreeImage returned FISupport.badLibrary and no version of FreeImage successfully loaded
• a member of FISupport indicating the version of FreeImage that successfully loaded. When loadFreeImage returns FISupport.badLibrary, this will be a version number lower than that configured at compile time. Otherwise, it will be the same as the manifest constant fiSupport.

The function isFreeImageLoaded returns true if any version of FreeImage was successfully loaded and false otherwise.

Following are the supported versions of FreeImage, the corresponding version IDs to pass to the compiler, and the corresponding FISupport members.

Library & Version	Version ID	FISupport Member
FreeImage 3.17	FI_317 (Default)	FISupport.fi317
FreeImage 3.18	FI_318	FISupport.fi318

The static binding

The static binding has a link-time dependency on either the shared or the static FreeImage library. On Windows, you can link with the static library or, to use the shared library (freeimage.dll), with the import library. On other systems, you can link with either the static library or directly with the shared library. This requires the FreeImage development package be installed on your system at compile time, either by compiling the FreeImage source yourself, downloading the FreeImage precompiled binaries for Windows, or installing via a system package manager. See the FreeImage download page for details.

When linking with the static library, there is no run-time dependency on FreeImage. When linking with the shared library (or the import library on Windows), the run-time dependency is the same as the dynamic binding, the difference being that the shared library is no longer loaded manually—loading is handled automatically by the system when the program is launched.

Enabling the static binding can be done in two ways.

Via the compiler's -version switch or DUB's versions directive

Pass the BindFI_Static version to the compiler and link with the appropriate library.

Using the compiler command line or a build system that doesn't support DUB, the -version=BindFI_Static option should be passed to the compiler when building your program. All of the required C libraries, as well as the bindbc-freeimage and bindbc-loader static libraries, must also be passed to the compiler on the command line or via your build system's configuration.

Using DUB, set the BindFI_Static version via its versions directive and the required libraries in the libs directive. For example:

dub.json

"dependencies": {
    "bindbc-freeimage": "~>1.0.0"
},
"versions": ["BindFI_Static"],
"libs": ["freeimage"]

dub.sdl

dependency "bindbc-freeimage" version="~>1.0.0"
versions "BindFI_Static"
libs "freeimage"

The above example only links to the FreeImage library, meaning it is linking with either the shared library or, on Windows, the import library for the DLL. When linking with the FreeImage static library, any dependencies it has must also be added to the libs directive.

Via DUB subconfigurations

Instead of using DUB's versions directive, a subConfiguration can be used. Enable the static subconfiguration for the bindbc-freeimage dependency:

dub.json

"dependencies": {
    "bindbc-freeimage": "~>1.0.0"
},
"subConfigurations": {
    "bindbc-freeimage": "static"
},
"libs": ["freeimage"]

dub.sdl

dependency "bindbc-freeimage" version="~>1.0.0"
subConfiguration "bindbc-freeimage" "static"
libs "freeimage"

This has the benefit that it completely excludes from the build any source modules related to the dynamic binding, i.e. they will never be passed to the compiler. When linking with the FreeImage static library, its dependencies must still also be added to the libs directive.

betterC support

betterC support is enabled via the dynamicBC and staticBC subconfigurations, for dynamic and static bindings respectively. To enable the static binding with -betterC support:

dub.json

"dependencies": {
    "bindbc-freeimage": "~>1.0.0"
},
"subConfigurations": {
    "bindbc-freeimage": "staticBC"
},
"libs": ["freeimage"]

dub.sdl

dependency "bindbc-freeimage" version="~>1.0.0"
subConfiguration "bindbc-freeimage" "staticBC"
libs "freeimage"

When not using DUB to manage your project, first use DUB to compile the BindBC libraries with the dynamicBC or staticBC configuration, then pass -betterC to the compiler when building your project.

Support for the JPEGTransform* functions

On some platforms, the following functions may be disabled by default in the binaries distributed via the system package manager:

• FreeImage_JPEGTransform
• FreeImage_JPEGTransformU
• FreeImage_JPEGCrop
• FreeImage_JPEGCropU
• FreeImage_JPEGTransformFromHandle
• FreeImage_JPEGTransformCombined
• FreeImage_JPEGTransformCombinedU
• FreeImage_JPEGTransformCombinedFromMemory

binbc-freeimage excludes these functions by default. If your application requires these functions, there are a few steps to take.

First, add the version BindFI_JPEGTransform to your DUB package configuration or compiler command line.

dub.json

"versions": ["BindFI_JPEGTransform"],

dub.sdl

versions "BindFI_JPEGTransform"

Next, either ship your application with a version of the FreeImage shared library that supports these functions or inform your users they'll need to compile or install a version that does.

Finally, for robustness, you may want to use the bindbc-loader error handling API to filter any errors that arise when these functions are missing so that you may present an error message to your users informing them how to install a properly compiled version of the FreeImage shared library.