IG_load_thumbnail

This function loads a thumbnail from the file specified by a file handle.

Declaration:

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AT_ERRCOUNT ACCUAPI IG_load_thumbnail_FD( AT_INT fd, LONG lOffset, LPHIGEAR lphIGear );

Arguments:

Name	Type	Description
fd	AT_INT	Handle of the open file containing the image from which to load the thumbnail. This handle can be obtained from Microsoft Windows functions such as CreateFile(), and cast to AT_INT for passing to the function parameter. FILE pointers returned by functions such as fopen(), and file handles returned by functions such as _sopen_s() are not supported.
lOffset	LONG	Offset in file at which file image begins.
lphIGear	LPHIGEAR	Pointer to a HIGEAR variable to receive the handle.

Return Value:

Returns 0 if successful. Otherwise, returns the number of ImageGear errors that occurred during this function call.

Supported Raster Image Formats:

All pixel formats supported by ImageGear for C and C++.

Example:

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HIGEAR hIGear1 = 0; /* handle ret'd by IG_load_FD / HIGEAR hIGear2 = 0; / handle for thumbnail / HANDLE fd; / DOS File Descriptor / LONG lOffset; / offset to image in file / UINT nPageNum; / will be 0 for this call / AT_ERRCOUNT nErrcount; / to test for errors / fd = CreateFile(_T("picture.bmp"), GENERIC_READ, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL); if(fd != INVALID_HANDLE_VALUE) { nPageNum = 0; / not a multi-page file / lOffset = 0; / access file from start / / Load image, and obtain its HIGEAR handle: */ nErrcount = IG_load_FD((AT_INT)fd, lOffset, nPageNum, 0, &hIGear1 ); CloseHandle(fd); if(nErrcount == 0) { nErrcount = IG_load_thumbnail_FD((AT_INT)fd, lOffset, &hIGear2 ); } //... // Destroy images if(IG_image_is_valid(hIGear1)) { IG_image_delete(hIGear1); } if(IG_image_is_valid(hIGear2)) { IG_image_delete(hIGear2); } }

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HIGEAR hIGear1 = 0;     /* handle ret'd by IG_load_FD  */
HIGEAR hIGear2 = 0;     /* handle for thumbnail  */
HANDLE fd;                /* DOS File Descriptor  */
LONG     lOffset;           /* offset to image in file */
UINT     nPageNum;          /* will be 0 for this call */
AT_ERRCOUNT nErrcount;        /* to test for errors  */

fd = CreateFile(_T("picture.bmp"), GENERIC_READ,
        0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

if(fd != INVALID_HANDLE_VALUE)
{
    nPageNum  = 0;          /* not a multi-page file  */
    lOffset    = 0;         /* access file from start */
    /* Load image, and obtain its HIGEAR handle:    */
    nErrcount = IG_load_FD((AT_INT)fd, lOffset, nPageNum, 0, &hIGear1 );
    CloseHandle(fd);
    if(nErrcount == 0)
    { 
        nErrcount = IG_load_thumbnail_FD((AT_INT)fd, lOffset, &hIGear2 ); 
    }

    //...

    // Destroy images
    if(IG_image_is_valid(hIGear1))
    {
        IG_image_delete(hIGear1);
    }
    if(IG_image_is_valid(hIGear2))
    {
        IG_image_delete(hIGear2);
    }
}

Remarks:

The handle of the resulting image is returned to the HIGEAR variable pointed to by argument lphIGear. See also functions IG_load_thumbnail, and IG_save_thumbnail_set.