Load, show and convert miscellaneous file-formats using freeimage

• Download binary - 310 Kb (executable, freeimage-dll)
• Download source - 362 Kb (MFC-project, freeimage-dll, lib and header)

Introduction

In this article I want to show the following:

• load, convert and save various file formats (tif, bmp, jpeg, ico, jif, jfif, koa, pcd, pcx, png, pbm, pgm, ppm, ras, targa, tga)
• supporting multipage-images
• convert color-model (1bit ... 256 colors ... 16 bit ... 24 bit ... 32 bit)
• tile the images in horizontal or vertical order
• integrating freeimage in own projects
• a sample mdi application with some simple techniques like
  explorer-drag/drop
  a file-open-box for selecting multiple files
  background-threads for long-duration-tasks (e.g. loading images)
• zooming and scrollbars
• improved drawing-speed (using the clipping region)
• drag/drop from explorer

The Graphics-Suite

Opening and Saving

These functions are implemented using freeimage (see below). The code for opening and saving looks is very simple and looks like this (simplified):

BOOL CGraphicSuiteDoc::OnOpenDocument(LPCTSTR lpszPathName) 
{
    FREE_IMAGE_FORMAT    fif;
    
    DeleteContents();

    fif = FreeImage_GetFIFFromFilename(lpszPathName);
    if( fif != FIF_UNKNOWN )
        m_handleFI = FreeImage_Load(fif, lpszPathName);
    
    return (m_handleFI != NULL);
}

void CGraphicSuiteDoc::OnFileSaveAs() 
{
    CString           filter,
                      szDest;
    DWORD             dwFlags = OFN_OVERWRITEPROMPT | 
                                OFN_EXPLORER | 
                                OFN_LONGNAMES | 
                                OFN_PATHMUSTEXIST | 
                                OFN_HIDEREADONLY;
    FREE_IMAGE_FORMAT fif;
    BOOL              bErg;

    filter.LoadString(IDS_STRING_FILTER_GRAPHICS);
    
    CFileDialog    dlg(FALSE, NULL, szDest, dwFlags, filter, 
                       AfxGetMainWnd());

    if(  dlg.DoModal() != IDOK)
        return;
    
    fif = FreeImage_GetFIFFromFilename(dlg.GetPathName());
    if( fif == FIF_UNKNOWN )
    {
        AfxMessageBox("Unknown type.");
        return;
    }

    bErg = FALSE;
    try
    {
        bErg = FreeImage_Save(fif, m_handleFI, dlg.GetPathName());
    }
    catch(...)
    {
    }
    
    if( !bErg )
        AfxMessageBox("Failed saving !");
}

Display and Printing

The MDI-sample uses freeimage to do all the image-stuff, except the display. In this sample the display is handled using the API-function StretchDIBits. In the real-code also the clip-box is used in order only to extract the pixels that have to be repainted. Thus the code shown here is a little simplified to the the technique. I've choosen mapping-mode MM_HIMETRIC, because then you can print the images using the correct resolution and metrics.

void CGraphicSuiteView::OnDraw(CDC* pDC)
{
    CGraphicSuiteDoc    *pDoc = GetDocument();
    
    pDC->SetMapMode(MM_HIMETRIC);

    double dpiX   = FreeImage_GetDotsPerMeterX(pDoc->m_handleFI),
           dpiY   = FreeImage_GetDotsPerMeterY(pDoc->m_handleFI),
           width  = FreeImage_GetWidth(pDoc->m_handleFI),
           height = FreeImage_GetHeight(pDoc->m_handleFI),
           sizeX,    // 1/100 mm == HIMETRIC

           sizeY;
    BYTE    *pData    = FreeImage_GetBits(pDoc->m_handleFI);

    if( dpiX==0.0 )    dpiX = 72.0 * 100.0 / 2.54;
    if( dpiY==0.0 )    dpiY = 72.0 * 100.0 / 2.54;

    sizeX = m_Zoom * 100.0 * 1000.0 * width  / dpiX;
    sizeY = m_Zoom * 100.0 * 1000.0 * height / dpiY;

    // stretched 

    ::StretchDIBits(pDC->m_hDC,
        // x-y-coord of destination upper-left corner

        sizeX, -sizeY,                       
        // width-height of destination rectangle

        (int)(sizeX+0.5), -(int)(sizeY+0.5), 
        // x-y-coord of source upper-left corner

        0, 0,                                
        // width-height of source rectangle

        (int)(width+0.5), (int)(height+0.5), 
        pData,                               // bitmap bits

        FreeImage_GetInfo(pDoc->m_handleFI),    // bitmap data

        DIB_RGB_COLORS,                      // usage options

        SRCCOPY                              // raster operation code

        );
}

.. or use (see code for how the parameters are to be initialized)

    // no stretching

    ::SetDIBitsToDevice(
        pDC->m_hDC, // handle to DC

        xDst, yDst, // x-y-coord of destination upper-left corner

        dxSrc, dySrc, // width-height of source rectangle

        xSrc, ySrc, // x-y-coord of source upper-left corner

        0,//uStartScan,// first scan line in array

        FreeImage_GetHeight(pFIBitmap), // number of scan lines

        FreeImage_GetBits(pFIBitmap), // array of DIB bits

        FreeImage_GetInfo(pFIBitmap), // bitmap information

        DIB_RGB_COLORS); // RGB or palette indexes

Image information

To complete the program, the relevant image information is shown in a dialog:

FreeImage

(Text taken from the freeimage-introduction ! )

What is freeimage ?

FreeImage is an Open Source library project for developers who would like to support popular graphics image formats like BMP, JPEG, TIFF and PCX and others as needed by today's multimedia applications. The libraries comes in two versions: a binary distribution that can be linked against any 32-bit c++ compiler and a source distribution. Workspace files for Microsoft Visual C++ 6 are provided, as well as makefiles for linux.

Features of freeimage

• Ease of use. The library has been designed to be extremely simple in use. Our motto is: make difficult things simple instead of simple things difficult.
• Not limited to the local PC. The unique FreeImageIO structure makes it possible to load your images from virtually anywhere. Possibilities include standalone files, memory, cabinet files and the Internet, all this without recompiling the library!
• Plugin driven. The internal engine is made completely modular using a clever plugin system. Easily Write new plugins and store them in DLL files or embed the plugins directly into your application!
• Color conversion. FreeImage provides many functions to convert a bitmap from one bitdepth to another.
• Directly access bitmap bits and palette. Functions are provided which allow you to directly access the bitmap palette (if available) and bitmap bits.
• Written in portable C++, should compile on all 32 bit Windows systems as well as under Linux and Solaris. Full source code provided.
• Open Source Dual-License. You can choose the license that has the most advantages for you: Use the liberal FreeImage Public License to use FreeImage commercially or the GNU General Public License to use FreeImage into your open source project.
• Easily integrates into DirectX and OpenGL. Only a minimum of programming is necessary to store a FreeImage bitmap into a DirectDraw surface. Or use FreeImage to load your Direct3D/OpenGL textures.
• Provides many test programs to "show-off" the library.
• Supports many formats, such as:
  • BMP files [reading, writing]
  • Dr. Halo files [reading] **
  • ICO files [reading]
  • IFF files [reading]
  • JBIG [reading, writing] *
  • JNG files [reading]
  • JPEG/JIF files [reading, writing]
  • KOALA files [reading]
  • LBM files [reading]
  • Kodak PhotoCD files [reading]
  • MNG files [reading]
  • PCX files [reading]
  • PBM files [reading, writing]
  • PGM files [reading, writing]
  • PNG files [reading, writing]
  • PPM files [reading, writing]
  • PhotoShop files [reading]
  • Sun RAS files [reading]
  • TARGA files [reading]
  • TIFF files [reading, writing]
  • WBMP files [reading, writing]

  * only via external plugin
  ** only grayscale

Freeimags-Internals

Freeimage loads the various file-formats using different libraries, e.g. libtiff or zlib. When loading a file, the data is converted internally using the structure BITMAPINFO from the Win32-API (even when it is compiled under linux). This approach makes it easy converting from format x to format y. To support a specific file-format there are needed only 2 converters, one for loading from the file to a BITMAPINFO and the other for saving from BITMAPINFO into the file:

FIBITMAP         *FreeImage_Load(FREE_IMAGE_FORMAT fif, 
                                 const char *filename, int flags);
BOOL              FreeImage_Save(FREE_IMAGE_FORMAT fif, FIBITMAP *dib, 
                                 const char *filename, int flags);
FREE_IMAGE_FORMAT FreeImage_GetFIFFromFilename(const char *filename);

If you need more infos, download the source, want to discuss or, even better, want to develop additional features, you can visit the freeimage homepage.

Some programming hints can be found here: FreeImage FAQ.

Credits

The code was written using:

History

Coming versions (maybe)

• edit ontop of images
• activeX Control
• console für batch ?
• I plan to continue the Graphics-Suite to display vector-data on top of the images. The vector-information is stored in SVG-files. For more info about SVG see w3c and abobe.