challenged by GDI+

[Chris Holbrook]

A couple of years ago I cobbled together (mostly from examples here) enough GDI+ code to allow basic picture-handling and it has served my purpose until today (see code below). Now I need to extend it so as to capture the image - somehow - after it has been read from a JPG/PNG/BMP/GIF/TIF/ICO file, so that I can store it into a database. It would be childs play to read the file and store a copy of that in the database, but then to redisplay it I would have to write it out again, which is a bit daft.

So the challenge is a) to store it (I need a pointer and a length for this) and b) to restore the stored object via a GDI+ function in order to redisplay the picture.

Because the initial window size could be small, storing and reusing the initial bitmap might not be a good idea.

Any ideas?

'--------------------------------------------------------------------------------
' MiniGDIP.inc  placed in public domain by Chris Holbrook June 2006
'
' based on code by Messrs Roca, Terrier, Schullian, Walker & others, thanks to Simon Morgan for debugging.
' modified Jan 2008: globals no longer used
'--------------------------------------------------------------------------------
'GDIP CONSTANTS
%QualityModeHigh = 2       ' Best rendering quality
%UnitPixel       = 2 ' Each unit is one device pixel.
'--------------------------------------------------------------------------------
'
TYPE GdiplusStartupInput
   GdiplusVersion AS DWORD             '// Must be 1
   DebugEventCallback AS DWORD         '// Ignored on free builds
   SuppressBackgroundThread AS LONG    '// FALSE unless you're prepared to call
                                       '// the hook/unhook functions properly
   SuppressExternalCodecs AS LONG      '// FALSE unless you want GDI+ only to use
                                       '// its internal image codecs.
END TYPE                                                                                    bitblt
'
'-----------------------------------------------------------------------------------------------------------------------
'
TYPE GdiplusStartupOutput
'  // The following 2 fields are NULL if SuppressBackgroundThread is FALSE.
'  // Otherwise, they are functions which must be called appropriately to
'  // replace the background thread.
'  //
'  // These should be called on the application's main message loop - i.e.
'  // a message loop which is active for the lifetime of GDI+.
'  // "NotificationHook" should be called before starting the loop,
'  // and "NotificationUnhook" should be called after the loop ends.
   NotificationHook AS DWORD
   NotificationUnhook AS DWORD
END TYPE
'
'-----------------------------------------------------------------------------------------------------------------------
'
TYPE ImageCodecInfo
   ClassID AS GUID            '// CLSID. Codec identifier
   FormatID AS GUID           '// GUID. File format identifier
   CodecName AS DWORD         '// WCHAR*. Pointer to a null-terminated string
                              '// that contains the codec name
   DllName AS DWORD           '// WCHAR*. Pointer to a null-terminated string
                              '// that contains the path name of the DLL in
                              '// which the codec resides. If the codec is not
                              '// a DLL, this pointer is NULL
   FormatDescription AS DWORD '// WCHAR*. Pointer to a null-terminated string
                              '// that contains the name of the format used by the codec
   FilenameExtension AS DWORD '// WCHAR*. Pointer to a null-terminated string
                              '// that contains all file-name extensions associated
                              '// with the codec. The extensions are separated with semicolons.
   MimeType AS DWORD          '// WCHAR*. Pointer to a null-terminated string
                              '// that contains the mime type of the codec
   Flags AS DWORD             '// Combination of flags from the ImageCodecFlags enumeration
   Version AS DWORD           '// Integer that indicates the version of the codec
   SigCount AS DWORD          '// Integer that indicates the number of signatures
                              '// used by the file format associated with the codec
   SigSize AS DWORD           '// Integer that indicates the number of bytes of each signature
   SigPattern AS DWORD        '// BYTE*. Pointer to an array of bytes that contains
                              '// the pattern for each signature
   SigMask AS DWORD           '// BYTE*. Pointer to an array of bytes that contains
                              '// the mask for each signature
END TYPE
'-----------------------------------------------------------------------------------------------------------------------
'
DECLARE FUNCTION GdipSetInterpolationMode LIB "gdiplus.dll" ALIAS "GdipSetInterpolationMode" (BYVAL graphics AS LONG, BYVAL interpolation AS LONG) AS LONG

DECLARE FUNCTION GdipCreateBitmapFromHBITMAP LIB "gdiplus.dll" ALIAS "GdipCreateBitmapFromHBITMAP" (BYVAL hbm AS LONG, BYVAL hpal AS LONG, nBitmap AS LONG) AS LONG

DECLARE FUNCTION GdipDrawImageRectI LIB "gdiplus.dll" ALIAS "GdipDrawImageRectI" (BYVAL graphics AS LONG, BYVAL nImage AS LONG, BYVAL x AS LONG, BYVAL y AS LONG, BYVAL nWidth AS LONG, BYVAL Height AS LONG) AS LONG

DECLARE FUNCTION GdipGetImageWidth LIB "gdiplus.dll" ALIAS "GdipGetImageWidth" (BYVAL nImage AS LONG, nWidth AS LONG) AS LONG
DECLARE FUNCTION GdipGetImageHeight LIB "gdiplus.dll" ALIAS "GdipGetImageHeight" (BYVAL nImage AS LONG, Height AS LONG) AS LONG

DECLARE FUNCTION GdipDeleteGraphics LIB "gdiplus.dll" ALIAS "GdipDeleteGraphics" (BYVAL graphics AS LONG) AS LONG

DECLARE FUNCTION GdipGraphicsClear LIB "gdiplus.dll" ALIAS "GdipGraphicsClear" (BYVAL graphics AS LONG, BYVAL lColor AS LONG) AS LONG
DECLARE FUNCTION GdipCreateFromHWND LIB "gdiplus.dll" ALIAS "GdipCreateFromHWND" (BYVAL hwnd AS LONG, graphics AS LONG) AS LONG
DECLARE FUNCTION GdipCreateFromHDC LIB "gdiplus.dll" ALIAS "GdipCreateFromHDC" (BYVAL hdc AS LONG, graphics AS LONG) AS LONG

DECLARE FUNCTION GdipGetImagePixelFormat LIB "gdiplus.dll" ALIAS "GdipGetImagePixelFormat" _
            (BYVAL nImage AS LONG, PixelFormat AS LONG) AS LONG
DECLARE FUNCTION GdipGetImageDimension LIB "gdiplus.dll" ALIAS "GdipGetImageDimension" _
            (BYVAL nImage AS LONG, nWidth AS SINGLE, Height AS SINGLE) AS LONG
DECLARE FUNCTION GdipGetImageGraphicsContext LIB "gdiplus.dll" ALIAS "GdipGetImageGraphicsContext" _
            (BYVAL nImage AS LONG, graphics AS LONG) AS LONG
DECLARE FUNCTION GdiplusStartup LIB "GDIPLUS.DLL" ALIAS "GdiplusStartup" _
            (token AS DWORD, inputbuf AS GdiplusStartupInput, outputbuf AS GdiplusStartupOutput) AS LONG
DECLARE SUB GdiplusShutdown LIB "GDIPLUS.DLL" ALIAS "GdiplusShutdown" _
            (BYVAL token AS DWORD)
DECLARE FUNCTION GdipLoadImageFromFile LIB "GDIPLUS.DLL" ALIAS "GdipLoadImageFromFile" _
            (BYVAL flname AS STRING, lpImage AS DWORD) AS LONG
DECLARE FUNCTION GdipDisposeImage LIB "GDIPLUS.DLL" ALIAS "GdipDisposeImage" _
            (BYVAL lpImage AS DWORD) AS LONG
DECLARE FUNCTION GdipGetImageEncodersSize LIB "GDIPLUS.DLL" ALIAS "GdipGetImageEncodersSize" _
            (numEncoders AS DWORD, nSize AS DWORD) AS LONG
DECLARE FUNCTION GdipGetImageEncoders LIB "GDIPLUS.DLL" ALIAS "GdipGetImageEncoders" _
            (BYVAL numEncoders AS DWORD, BYVAL nSize AS DWORD, BYVAL lpEncoders AS DWORD) AS LONG
DECLARE FUNCTION GdipSaveImageToFile LIB "GDIPLUS.DLL" ALIAS "GdipSaveImageToFile" _
            (BYVAL lpImage AS DWORD, BYVAL flname AS STRING, clsidEncoder AS GUID, _
             OPTIONAL BYVAL EncoderParams AS DWORD) AS LONG
DECLARE FUNCTION GdipCreateBitmapFromScan0 LIB "gdiplus.dll" ALIAS "GdipCreateBitmapFromScan0" _
            (BYVAL nWidth AS LONG, BYVAL Height AS LONG, BYVAL stride AS LONG, BYVAL PixelFormat AS LONG, _
             scan0 AS ANY, nBitmap AS LONG) AS LONG
DECLARE FUNCTION GdipGetInterpolationMode LIB "gdiplus.dll" ALIAS "GdipGetInterpolationMode" _
            (BYVAL graphics AS LONG, interpolation AS LONG) AS LONG
DECLARE FUNCTION GdipDrawImageRectRectI LIB "gdiplus.dll" ALIAS "GdipDrawImageRectRectI" _
            (BYVAL graphics AS LONG, BYVAL nImage AS LONG, BYVAL dstx AS LONG, BYVAL dsty AS LONG, _
             BYVAL dstwidth AS LONG,  BYVAL dstheight AS LONG, BYVAL srcx AS LONG, BYVAL srcy AS LONG, _
             BYVAL srcwidth AS LONG, BYVAL srcheight AS LONG, BYVAL srcUnit AS LONG, _
             OPTIONAL BYVAL imageAttributes AS LONG, OPTIONAL BYVAL pCALLBACK AS LONG, _
             OPTIONAL BYVAL callbackData AS LONG) AS LONG
DECLARE FUNCTION GdipGetSmoothingMode LIB "gdiplus.dll" ALIAS "GdipGetSmoothingMode" _
            (BYVAL graphics AS LONG, SmoothingMd AS LONG) AS LONG
DECLARE SUB skIconise (BYVAL xPic AS LONG, BYVAL yPic AS LONG,            _ picture dimensions
               BYVAL xCell AS LONG, BYVAL yCell AS LONG,          _ FRAME dimensions
               BYREF xOfs AS LONG, BYREF yOfs AS LONG,            _ calc'd offset in frame
               BYREF xSize AS LONG, BYREF ySize AS LONG)   ' thumbnail dimensions
'
'-----------------------------------------------------------------------------------------------------------------------
'
FUNCTION ReadUnicodeString (BYVAL lp AS DWORD) AS STRING
   LOCAL p AS BYTE PTR, s AS STRING
   p = lp                             '// Pointer to the string
   IF p = %Null THEN EXIT FUNCTION    '// Null pointer
   WHILE CHR$(@p) <> $NUL
      s = s + CHR$(@p)
      p = p + 2                       '// Unicode strings require two bytes per character
   WEND
   FUNCTION = s
END FUNCTION
'
'-----------------------------------------------------------------------------------------------------------------------
'
' ==========================================================================
' GetEncoderClsid
' The function GetEncoderClsid in the following example receives the MIME
' type of an encoder and returns the class identifier (CLSID) of that encoder.
' The MIME types of the encoders built into GDI+ are as follows:
'   image/bmp
'   image/jpeg
'   image/gif
'   image/tiff
'   image/png
' ==========================================================================
FUNCTION GetEncoderClsid (BYVAL sMimeType AS STRING) AS STRING
   DIM pImageCodecInfo AS ImageCodecInfo PTR
   LOCAL numEncoders AS DWORD, nSize AS DWORD
   LOCAL lRslt AS LONG, i AS LONG, x AS LONG
   LOCAL p AS BYTE PTR, s AS STRING
   LOCAL nSigCount AS LONG, nSigSize AS LONG
   sMimeType = UCASE$(sMimeType)
   lRslt = GdipGetImageEncodersSize(numEncoders, nSize)
   REDIM buffer(nSize - 1) AS BYTE
   pImageCodecInfo = VARPTR(buffer(0))
   lRslt = GdipGetImageEncoders(numEncoders, nSize, pImageCodecInfo)
   IF lRslt = 0 THEN
      FOR i = 1 TO numEncoders
         IF INSTR(UCASE$(ReadUnicodeString(@pImageCodecInfo.MimeType)), sMimeType) THEN
            FUNCTION = GUIDTXT$(@pImageCodecInfo.ClassID)
            EXIT FOR
         END IF
         INCR pImageCodecInfo       '// Increments pointer
      NEXT
   END IF
END FUNCTION
'
'-----------------------------------------------------------------------------------------------------------------------
' write resized image to file and/or window. If filename is blank, file will not be created.
'                                            If window handle is null, window will not be painted.
FUNCTION ResizeImage (picpath AS STRING, destpath AS STRING, hW AS DWORD, maxwidth AS DWORD, maxheight AS DWORD) AS LONG
    LOCAL origwidth AS SINGLE
    LOCAL origheight AS SINGLE
    LOCAL lPixelFormat AS LONG
    LOCAL s AS STRING
    LOCAL EncoderClSID AS GUID
    LOCAL extn AS STRING
    LOCAL imagestyle AS STRING
    LOCAL OfsX, OfsY, Tx, Ty AS LONG
    LOCAL hbitmap, himage, graphics AS DWORD
    '

    IF destpath <> "" THEN ' if destpath is not specified we still load the global image
        extn = UCASE$(PARSE$(destpath,".",-1))
        SELECT CASE CONST$ extn
             CASE "BMP"         : imagestyle = "image/bmp"
             CASE "EMF"         : imagestyle = "image/x-emf"
             CASE "GIF"         : imagestyle = "image/gif"
             CASE "ICO"         : imagestyle = "image/x-icon"
             CASE "JPG", "JPEG" : imagestyle = "image/jpeg"
             CASE "PNG"         : imagestyle = "image/png"
             CASE "TIF", "TIFF" : imagestyle = "image/tiff"
             CASE "WMF"         : imagestyle = "image/x-wmf"
             CASE ELSE
                 ' return image handle value of zero to indicate failure
                  EXIT FUNCTION
        END SELECT
    END IF
    '
    GDIPLoadImageFromFile UCODE$(picPath), hImage
    '
    IF hImage = 0 THEN
        ' return image handle value of zero to indicate failure
        EXIT FUNCTION
    END IF
    '
    GdipGetImageDimension hImage, origwidth, origheight
    '
    skIconise ( origwidth, origheight, maxwidth, maxheight, ofsX, ofsY, tX, tY)
    '
    GdipGetImagePixelFormat hImage, lPixelFormat

    ' create right-size bitmap
    GdipCreateBitmapFromScan0 tX, tY, 0, lPixelFormat, BYVAL 0&, hBitmap
    ' get graphics handle to bitmap
    GdipGetImageGraphicsContext hBitmap, graphics
    GdipSetInterpolationMode graphics, %QualityModeHigh
    ' drop image into graphics object
    GdipDrawImageRectRectI graphics, hImage, 0, 0, tX, tY, 0, 0, origwidth, origheight, %UnitPixel
    ' save resized image to file if output filename is not null
    IF destpath <> "" THEN
        s = GetEncoderClsid(imagestyle)
        EncoderCLSID = GUID$(s)
        GdipSaveImageToFile hbitmap, UCODE$(DestPath), EncoderCLSID, %NULL
    END IF
    ' get rid of unwanted GDI objects
    CALL GdipDeleteGraphics(graphics)
    deleteobject hbitmap
    FUNCTION = himage
END FUNCTION
'
'-------------------------------------------------------------------------------------------------------
' Computes location and size to stretch a bitmap preserving its aspect.
'
SUB skIconise (BYVAL xPic AS LONG, BYVAL yPic AS LONG,            _ picture dimensions
               BYVAL xCell AS LONG, BYVAL yCell AS LONG,          _ FRAME dimensions
               BYREF xOfs AS LONG, BYREF yOfs AS LONG,            _ calc'd offset in frame
               BYREF xSize AS LONG, BYREF ySize AS LONG) EXPORT   ' thumbnail dimensions
  LOCAL SCALE AS SINGLE

    IF xPIC& THEN scale! = xCell& / xPic&
    IF scale! > 1 THEN scale! = 1
    xSize& = xPic& * scale!: ySize& = yPic& * scale!
  ' In case Height > 150 compute new scale factor
    IF ySize& > yCell& THEN
       IF yPic& THEN scale! = yCell& / yPic&
       xSize& = xPic& * scale!: ySize& = yPic& * scale!
    END IF
    xOfs& = (xCell& - xSize&) \ 2
    yOfs& = (yCell& - ySize&) \ 2
END SUB

[Chris Holbrook]

Since I first looked for GDI+ info a couple of years ago a lot more stuff has appeared on the www. For strictly PB people Jose Roca's forums are a good place to look.

So far it looks as if half my question has been answered by an example of Jose Roca's using GdipCreateBitmapFromStream. I can modify this to load the image which I store in my database.

Haven't yet worked out how to save the image though. The mechanics of getting it in and out of the blob field are not a problem, just how to get from a valid image handle to a memory address and byte count to create the stored form of the image.

[Edwin Knoppert]

The stream is an IStream interface.
Fairly simple to use..
A simple 'gather all data into a buffer' situation.

[Chris Holbrook]

Following examples by Jose Roca and Kev Peel, I have discovered that the GDI+ bitmap functions return bitmap handles which are not compatible with the GDI ones. Fortunately there are conversion functions in GDI+, so the bitmap can eventually be manipulated using GetDIBits, for example.

From my testing code - sorry it's not compilable but I'm in a hurry!

    ' create a memory DC
    hDC = CreateCompatibleDC ( 0 )
    ' Create a GDIP+ Bitmap object from a JPEG file.
    lresult = GdipCreateBitmapFromFile(UCODE$(gsPicPath), pBitmap)
    ' get a GDI bitmap handle for it
    lresult = GdipCreateHBITMAPFromBitmap(pBitmap, hbitmap, BYVAL -1)
    ' get bitmap stats into the BMINFO structure
    bitbuffer = STRING$(SIZEOF(BITMAPINFOHEADER), $NUL)
    pBMINFO = STRPTR(bitbuffer)
    @pBMINFO.biSize = SIZEOF(BITMAPINFOHEADER)

    lresult = GetDIBits(hDC, hBitMap, 0, 0, BYVAL %NULL, BYVAL pBMINFO, %DIB_RGB_COLORS)

    ?  "result " + STR$(lresult) + $CRLF + _
       "bitmap " + STR$(hbitmap) + $CRLF + _
       "size   " + STR$(@pBMINFO.bisize) + $CRLF + _
       "width  " + STR$(@pBMINFO.biwidth) + $CRLF + _
       "height " + STR$(@pBMINFO.biheight) + $CRLF + _
       "planes " + STR$(@pBMINFO.biplanes) + $CRLF + _
       "bits per pixel               " + STR$(@pBMINFO.bibitcount) + $CRLF + _
       "compression                  " + STR$(@pBMINFO.bicompression) + $CRLF + _
       "size of image(bytes)         " + STR$(@pBMINFO.bisizeimage) + $CRLF + _
       "pixels per meter horizontal  " + STR$(@pBMINFO.biXPelsPerMeter) + $CRLF + _
       "pixels per meter vertical    " + STR$(@pBMINFO.biYPelsPerMeter) + $CRLF + _
       "no of color indices used     " + STR$(@pBMINFO.biClrUsed) + $CRLF + _
       "no of important color indices" + STR$(@pBMINFO.biClrImportant)

[Chris Holbrook]

The stream is an IStream interface.
Fairly simple to use..
A simple 'gather all data into a buffer' situation.

Is the format of the image saved by GdiPSaveImageToStream the same as the image format on disc, I wonder? Or is it a generic format?

If the image is saved to a stream, the length is not returned*, any ideas how to derive the length (size) of the image written to a stream?

Good compilable example code by Messrs Terrier & Roca for reading from an Istream using GdipLoadImageFromStream.

* most GDIplus functions appear to return either zero for success, or an error code. I have posted an application including an error code list (it's from Jose Roca's forum) on the Source Code forum.

[José Roca]

If you save it to disk as a stream, then you will have to load it using GdipLoadImageFromStream. This function returns an Image handle, that you can use with all the functions that accept such and handle, like GdipGetImageWidth and GdipGetImageHeight.

[Chris Holbrook]

If you save it to disk as a stream...

There are the functions GdipSaveImageToStream and GdipSaveImageToFile. Or do you mean that there is a function to write a stream to a file? Could not find it in the structured storage stuff.

(later) OK, I've found IStream_Stat, which gives cbsize, so can use the stream as a buffer, then

FILE            <<<<<<< APP >>>>>>>       DB      <<<<<<<< APP >>>>>>>
image file -> image handle -> istream -> blob -> istream -> image handle
                    |                                           |
                    +-------------------------------------------+
                                         |
                                     show image

[José Roca]

Or do you mean that there is a function to write a stream to a file? Could not find it in the structured storage stuff.

No, you have to open or create an storage file with StgCreateStorageEx, create an stream in it with IStorage_CreateStream and write the bytes in it. Later, you can reopen the storage file and get a pointer to the stream with IStorage_OpenStream, pointer that you can pass to GdipLoadImageFromStream to load the stream as a GDI+ image.