=====Loading a GIF or JPEG image=====

//by Richard Russell, September 2008//\\ \\  The main Help documentation describes how to [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwine.html#gifjpeg|display a GIF or JPEG image]] on the main output window, but you may wish to perform other operations on an image such as accessing its data or displaying it in a static control. In such cases you are likely to need a **handle** to the image.\\ \\  The function below operates in a similar way to **SYS "LoadImage"** except that it works with JPEG, GIF, BMP, ICO, EMF or WMF images. You can alternatively use the function **FNloadimagegdip2** listed at [[/Loading%20a%20PNG%20or%20TIFF%20image|Loading a PNG or TIFF image]] because that will load GIF and JPEG images too, and gives better results when the image is very large or needs to be scaled.

<code bb4w>
        DEF FNloadimage(file$, RETURN cx%, RETURN cy%, par%)
        LOCAL iid{}, bmp{}, ix%, iy%, hbm%, hcopy%, pic%, ole%, olpp%, text%
        DIM iid{a%,b%,c%,d%}, text% LOCAL 513

        iid.a% = &7BF80980 : REM. 128-bit iid
        iid.b% = &101ABF32
        iid.c% = &AA00BB8B
        iid.d% = &AB0C3000

        SYS "MultiByteToWideChar", 0, 0, file$, -1, text%, 256

        SYS "LoadLibrary", "OLEAUT32.DLL" TO ole%
        SYS "GetProcAddress", ole%, "OleLoadPicturePath" TO olpp%
        IF olpp%=0 THEN = 0

        SYS olpp%, text%, 0, 0, 0, iid{}, ^pic% : REM. OleLoadPicturePath
        IF pic%=0 THEN = 0

        SYS !(!pic%+12), pic%, ^hbm% : REM. IPicture::get_Handle
        IF hbm%=0 THEN = 0

        DIM bmp{bmType%,bmWidth%,bmHeight%,bmWidthBytes%,bmPlanes{l&,h&}, \
        \       bmBitsPixel{l&,h&}, bmBits%}
        SYS "GetObject", hbm%, DIM(bmp{}), bmp{}

        ix% = bmp.bmWidth%
        iy% = bmp.bmHeight%

        IF cx%=0 cx% = ix%
        IF cy%=0 cy% = iy%

        IF par% THEN
          IF cx%/cy%>ix%/iy% cx% = cy%*ix%/iy% ELSE cy% = cx%*iy%/ix%
        ENDIF

        SYS "CopyImage", hbm%, 0, cx%, cy%, 0 TO hcopy%
        SYS "DeleteObject", hbm%
        SYS !(!pic%+8), pic% : REM. IPicture::Release

        = hcopy%
</code>

The parameters to the function are the filename (or URL) of the image, the required width and height (in pixels) and a flag to indicate whether you want the **aspect ratio** to be preserved or not. Note that a filename must contain the drive name (e.g. **C:**) to distinguish it from an internet URL. The returned value is a **handle** to the image, or zero if the image cannot be found or opened.\\ \\  If the required width and/or height values are supplied as zero then the actual width and/or height of the original image are used. Thus if a non-zero value is supplied for the width and zero is supplied for the height, the image will be scaled horizontally (if required) but not vertically; however if the **preserve aspect ratio** flag is set to TRUE, the then image //will// be scaled vertically to preserve the correct shape.\\ \\  The actual dimensions of the (possibly scaled) image are returned in the second and third parameters, therefore they must be supplied as **variables** rather than as **constants**. Thus if you don't want to scale the image call the function as follows

<code bb4w>
        cx% = 0
        cy% = 0
        himage% = FNloadimage(filename$, cx%, cy%, FALSE)
</code>

Alternatively if you are not interested in knowing the actual dimensions you can modify the function definition by removing the **RETURN** qualifiers:

<code bb4w>
        DEF FNloadimage(file$, cx%, cy%, par%)
</code>

With this modification you can supply constant values (e.g. 0) as parameters.\\ \\  When you have completely finished with the image you should delete the handle as follows:

<code bb4w>
        SYS "DeleteObject", himage%
</code>

To use the **FNloadimage** function to display an image in a **static control** see this [[/Displaying%20a%20JPEG%20or%20GIF%20in%20a%20picture%20box|article]].\\ \\  To access the data of the image you can use the **SYS "GetDIBits"** API as follows:

<code bb4w>
        cx% = 0
        cy% = 0
        himage% = FNloadimage(filename$, cx%, cy%, FALSE)

        DIM bmih{biSize%, biWidth%, biHeight%, biPlanes{l&,h&}, \
        \ biBitCount{l&,h&}, biCompression%, biSizeImage%, \
        \ biXPelsPerMeter%, biYPelsPerMeter%, biClrUsed%, \
        \ biClrImportant%}

        bmih.biSize% = DIM(bmih{})
        bmih.biWidth% = cx%
        bmih.biHeight% = -cy%
        bmih.biPlanes.l& = 1
        bmih.biBitCount.l& = 24
        bmih.biCompression% = 0
        bmih.biSizeImage% = ((cx%*(bmih.biBitCount.l& DIV 8) + 3) AND -4) * cy%

        DIM imagedata% bmih.biSizeImage%-1

        SYS "GetDIBits", @memhdc%, himage%, 0, cy%, imagedata%, bmih{}, 0 TO num%
        SYS "DeleteObject", himage%
        IF num% <> cy% ERROR 100, "GetDIBits failed"
</code>

This provides the image data in 'top-down' format as RGB triplets stored at **imagedata%**; if you require a different data format modify the members of the **bmih** structure accordingly. Note that each line of image data is always padded (if necessary) to a multiple of four bytes.\\ \\  If the image data may be too large to be stored on the heap (possibly with **HIMEM** increased) then you can instead allocate the memory using the Windows API:

<code bb4w>
        SYS "GlobalAlloc", &40, bmih.biSizeImage% TO imagedata%
        IF imagedata% = 0 ERROR 100, "Insufficient memory"
</code>

but in this case don't forget to free the memory later.