The Windows examples were checked with genuine FreeImage 3.18.0 DLLs on Win32 and Win64. Use an import archive that matches the DLL's actual export names as well as its bitness. The checked Win32 DLL exports names such as _FreeImage_GetVersion@0. An archive that looks up FreeImage_GetVersion@0 instead can link successfully and then fail to load. Generate the archive from the real DLL with gendef and dlltool while preserving the export aliases; no replacement function implementation is needed.

Pair FreeImage_Initialise and FreeImage_DeInitialise around the application-owned image lifetime. The FB loaders return an owned 32-bit buffer, which the caller releases with ImageDestroy. They request 32-bit storage explicitly, check the source and destination pitches and limit the output to 16 million pixels. For formats supporting FIF_LOAD_NOPIXELS, they inspect dimensions before loading the pixel data; other formats are checked after loading. Display that buffer in a matching 32-bit graphics mode.

The SDL1 example borrows the bitmap's pixels for its surface. It releases the surface before calling FreeImage_Unload. It expands one-bit and four-bit palettes to 32 bits, checks the 16-bit SDL1 pitch/rectangle limits, and rejects non-bitmap sample types. Its palette path for eight-bit images checks SDL_SetColors.

Here follows an example of using FreeImage in FreeBASIC. If using Windows you will require freeimage.dll which is available from the FreeImage site.

'' Code example for loading all common image types using FreeImage.
'' The example loads an image passed as a command line argument.

'' The function FI_Load returns a null pointer (0) if there was an error during
'' loading.  Otherwise it returns a 32-bit PUT compatible buffer.

#include "FreeImage.bi"
#include "crt.bi"
#include "fbgfx.bi"

Function FI_Load(filename As String) As Any Ptr
    If Len(filename) = 0 Then
        Return NULL
    End If

    '' Find out the image format
    Dim As FREE_IMAGE_FORMAT form = FreeImage_GetFileType(StrPtr(filename), 0)
    If form = FIF_UNKNOWN Then
        form = FreeImage_GetFIFFromFilename(StrPtr(filename))
    End If

    '' Exit if unknown
    If form = FIF_UNKNOWN Then
        Return NULL
    End If

    '' Always load jpegs accurately
    Dim As Long flags = 0
    If form = FIF_JPEG Then
        flags = JPEG_ACCURATE
    End If
    Const MAX_IMAGE_PIXELS = 16 * 1024 * 1024
    '' Inspect supported formats without acquiring their pixel buffer.
    If FreeImage_FIFSupportsNoPixels(form) Then
        Dim metadata As FIBITMAP Ptr = FreeImage_Load(form, filename, flags Or FIF_LOAD_NOPIXELS)
        If metadata = NULL Then Return NULL
        Dim metadata_width As ULong = FreeImage_GetWidth(metadata)
        Dim metadata_height As ULong = FreeImage_GetHeight(metadata)
        FreeImage_Unload(metadata)
        If metadata_width = 0 Or metadata_height = 0 Or _
            CULngInt(metadata_width) * metadata_height > MAX_IMAGE_PIXELS Then Return NULL
    End If

    '' Load the image into memory
    Dim As FIBITMAP Ptr image = FreeImage_Load(form, StrPtr(filename), flags)
    If image = NULL Then
        '' FreeImage failed to read in the image
        Return NULL
    End If

    '' Flip the image so it matches FB's coordinate system
    If FreeImage_FlipVertical(image) = 0 Then
        FreeImage_Unload image
        Return NULL
    End If

    '' Convert to 32 bits per pixel
    Dim As FIBITMAP Ptr image32 = FreeImage_ConvertTo32Bits(image)
    If image32 = NULL Then
        FreeImage_Unload image
        Return NULL
    End If

    '' Get the image's size
    Dim As UInteger w = FreeImage_GetWidth(image)
    Dim As UInteger h = FreeImage_GetHeight(image)
    '' Limit display output to 16 million pixels (64 MiB at 32 bpp).
    If w = 0 Or h = 0 OrElse CULngInt(w) * h > MAX_IMAGE_PIXELS Then
        FreeImage_Unload image32
        FreeImage_Unload image
        Return NULL
    End If

    '' Create an FB image of the same size
    Dim As fb.Image Ptr sprite = ImageCreate(w, h, 0, 32)
    If sprite = NULL Then
        FreeImage_Unload image32
        FreeImage_Unload image
        Return NULL
    End If

    Dim As Byte Ptr target = CPtr(Byte Ptr, sprite + 1)
    Dim As Integer target_pitch = sprite->pitch

    Dim As Byte Ptr source = FreeImage_GetBits(image32)
    If source = NULL Then
        ImageDestroy sprite
        FreeImage_Unload image32
        FreeImage_Unload image
        Return NULL
    End If

    Dim As Integer source_pitch = FreeImage_GetPitch(image32)
    If source_pitch < CULngInt(w) * 4 Or target_pitch < CULngInt(w) * 4 Then
        ImageDestroy sprite
        FreeImage_Unload image32
        FreeImage_Unload image
        Return NULL
    End If

    '' And copy over the pixels, row by row
    For y As Integer = 0 To (h - 1)
        memcpy(target + (y * target_pitch), _
               source + (y * source_pitch), _
               w * 4)
    Next

    FreeImage_Unload(image32)
    FreeImage_Unload(image)

    Return sprite
End Function

#ifndef IMAGE_EXAMPLE_NO_MAIN
If ScreenRes(640, 480, 32) <> 0 Then
    Print "Could not set the requested graphics mode"
    End 1
End If

Dim As String filename = Command(1)
FreeImage_Initialise()

Dim As Any Ptr image = FI_Load(filename)
If image <> 0 Then
    Put (0, 0), image
    ImageDestroy(image)
Else
    Print "Problem while loading file : " & filename
    FreeImage_DeInitialise()
    End 1
End If

Sleep
FreeImage_DeInitialise()
#endif

'' end of freeimage.bas