Example Image Transcoder Component

QuickTime 4 Reference

Example Image Transcoder Component

The example code in Listing 1 shows an image transcoder component. It converts an imaginary compressed data format `bgr ' to uncompressed RGB pixels. The transcoding process simply copies the source data to the destination and inverts each byte in the process. This example shows the format of how an image transcoder might work without getting into the details of a particular image transcoding operation.

Listing 1 An image transcoder component, converting a compressed data format to uncompressed RGB pixels



 
#include <ImageCompression.h>

pascal ComponentResult main(ComponentParameters *params, Handle storage );

pascal ComponentResult TestTranscoderBeginSequence (Handle storage, ImageDescriptionHandle 

srcDesc, ImageDescriptionHandle *dstDesc, void *data, long dataSize);



pascal ComponentResult TestTranscoderConvert (Handle storage, void *srcData, long srcDataSize, 

void **dstData, long *dstDataSize);



pascal ComponentResult TestTranscoderDisposeData (Handle storage, void *dstData);



pascal ComponentResult TestTranscoderEndSequence (Handle storage);



pascal ComponentResult main(ComponentParameters *params, Handle storage )

{

    ComponentFunctionUPP proc = nil;

    ComponentResult err = noErr;



    switch (params->what) {

        case kComponentOpenSelect:

        case kComponentCloseSelect:

            break;

        case kImageTranscoderBeginSequenceSelect:

            proc = (ComponentFunctionUPP) TestTranscoderBeginSequence;

            break;

        case kImageTranscoderConvertSelect:

            proc = (ComponentFunctionUPP)TestTranscoderConvert;

            break;

        case kImageTranscoderDisposeDataSelect:

            proc = (ComponentFunctionUPP) TestTranscoderDisposeData;

            break;

        case kImageTranscoderEndSequenceSelect:

            proc = (ComponentFunctionUPP) TestTranscoderEndSequence;

            break;

        default:

            err = badComponentSelect;

            break;

    }



    if (proc)

        err = CallComponentFunctionWithStorage(storage,

                        params, proc);



    return err;

}



pascal ComponentResult TestTranscoderBeginSequence (Handle storage, ImageDescriptionHandle 

srcDesc, ImageDescriptionHandle *dstDesc, void *data, long dataSize)

{

    *dstDesc = srcDesc;

    HandToHand((Handle *)dstDesc);

    (***dstDesc).cType = 'raw ';



    return noErr;

}



pascal ComponentResult TestTranscoderConvert (Handle storage, void *srcData, long srcDataSize, 

void **dstData, long *dstDataSize)

{

    Ptr p;

    OSErr err;



    if (!srcDataSize)

        return paramErr;



    p = NewPtr(srcDataSize);

    err = MemError();

    if (err) return err;

    {

    Ptr p1 = srcData, p2 = p;

    long counter = srcDataSize;

    while (counter--)

        *p2++ = ~*p1++;

    }



    *dstData = p;

    *dstDataSize = srcDataSize;



    return noErr;

}



pascal ComponentResult TestTranscoderDisposeData (Handle storage, void *dstData)

{

    DisposePtr((Ptr)dstData);



    return noErr;

}



pascal ComponentResult TestTranscoderEndSequence (Handle storage)

{

    return noErr;

}