Adobe XMP SDK項目應用（續2）

今日我想給給圖像的exif屬性裡面增加一個SoftWare屬性，毋庸置疑，最終是失敗而告終。在SDk上面糾纏了半日，直奔核心代碼而去，最終無功而返。問題的症結其實跟前幾日差不多，修改xmp資訊可以，但是修改exif資訊，就得付出慘痛的代價，不斷的調試...跟蹤...調試...跟蹤，問題點是跟蹤出來了，在函數ExportTIFF_StandardMappings裡面

static void
ExportTIFF_StandardMappings ( XMP_Uns8 ifd, TIFF_Manager * tiff, const SXMPMeta & xmp )
{
	const bool nativeEndian = tiff->IsNativeEndian();
	TIFF_Manager::TagInfo tagInfo;
	std::string xmpValue;
	XMP_OptionBits xmpForm;

	const TIFF_MappingToXMP * mappings = 0;

	if ( ifd == kTIFF_PrimaryIFD ) {
		mappings = sPrimaryIFDMappings;
	} else if ( ifd == kTIFF_ExifIFD ) {
		mappings = sExifIFDMappings;
	} else if ( ifd == kTIFF_GPSInfoIFD ) {
		mappings = sGPSInfoIFDMappings;
	} else {
		XMP_Throw ( "Invalid IFD for standard mappings", kXMPErr_InternalFailure );
	}

	for ( size_t i = 0; mappings[i].id != 0xFFFF; ++i ) {

		try {	// Don't let errors with one stop the others.

			const TIFF_MappingToXMP & mapInfo =  mappings[i];

			if ( mapInfo.exportMode == kExport_Never ) continue;
			if ( mapInfo.name[0] == 0 ) continue;	// Skip special mappings, handled higher up.

			bool haveTIFF = tiff->GetTag ( ifd, mapInfo.id, &tagInfo );
			if ( haveTIFF && (mapInfo.exportMode == kExport_InjectOnly) ) continue;
			
            {
				bool haveXMP = xmp.GetProperty(mapInfo.ns, mapInfo.name, &xmpValue, &xmpForm);
				if (!haveXMP) {

					if (haveTIFF && (mapInfo.exportMode == kExport_Always)) tiff->DeleteTag(ifd, mapInfo.id);

				}
				else {

					XMP_Assert(tagInfo.type != kTIFF_UndefinedType);	// These must have a special mapping.
					if (tagInfo.type == kTIFF_UndefinedType) continue;

					const bool mapSingle = ((mapInfo.count == 1) || (mapInfo.type == kTIFF_ASCIIType));
					if (mapSingle) {
						if (!XMP_PropIsSimple(xmpForm)) continue;	// ? Notify client?
						ExportSingleTIFF(tiff, ifd, mapInfo, nativeEndian, xmpValue);
					}
    				else {
						if (!XMP_PropIsArray(xmpForm)) continue;	// ? Notify client?
						ExportArrayTIFF(tiff, ifd, mapInfo, nativeEndian, xmp, mapInfo.ns, mapInfo.name);
					}
				}
			}

		} catch ( ... ) {

			// Do nothing, let other imports proceed.
			// ? Notify client?

		}

	}

}	// ExportTIFF_StandardMappings
           

程式首先已經從tag裡面擷取到了tagInfo（裡面包含了exif:SoftWare資訊），緊跟着就從xmp中去擷取屬性資訊，導緻的結果就是從tag擷取的資訊實際上沒有用到。修改方案如下(紅色部分為新增加内容)：

static void

ExportTIFF_StandardMappings ( XMP_Uns8 ifd, TIFF_Manager * tiff, const SXMPMeta & xmp )

{

    const bool nativeEndian = tiff->IsNativeEndian();

    TIFF_Manager::TagInfo tagInfo;

    std::string xmpValue;

    XMP_OptionBits xmpForm;

    const TIFF_MappingToXMP * mappings = 0;

    if ( ifd == kTIFF_PrimaryIFD ) {

        mappings = sPrimaryIFDMappings;

    } else if ( ifd == kTIFF_ExifIFD ) {

        mappings = sExifIFDMappings;

    } else if ( ifd == kTIFF_GPSInfoIFD ) {

        mappings = sGPSInfoIFDMappings;

    } else {

        XMP_Throw ( "Invalid IFD for standard mappings", kXMPErr_InternalFailure );

    }

    for ( size_t i = 0; mappings[i].id != 0xFFFF; ++i ) {

        try {    // Don't let errors with one stop the others.

            const TIFF_MappingToXMP & mapInfo =  mappings[i];

            if ( mapInfo.exportMode == kExport_Never ) continue;

            if ( mapInfo.name[0] == 0 ) continue;    // Skip special mappings, handled higher up.

            bool haveTIFF = tiff->GetTag ( ifd, mapInfo.id, &tagInfo );

            if ( haveTIFF && (mapInfo.exportMode == kExport_InjectOnly) ) continue;

            if (haveTIFF){

                XMP_Assert(tagInfo.type != kTIFF_UndefinedType);    // These must have a special mapping.

                if (tagInfo.type == kTIFF_UndefinedType) continue;

                if (tagInfo.type == kTIFF_ASCIIType)

                    xmpValue = (const char*)tagInfo.dataPtr;

                ExportSingleTIFF(tiff, ifd, mapInfo, nativeEndian, xmpValue);

            }

            else {

                bool haveXMP = xmp.GetProperty(mapInfo.ns, mapInfo.name, &xmpValue, &xmpForm);

                if (!haveXMP) {

                    if (haveTIFF && (mapInfo.exportMode == kExport_Always)) tiff->DeleteTag(ifd, mapInfo.id);

                }

                else {

                    XMP_Assert(tagInfo.type != kTIFF_UndefinedType);    // These must have a special mapping.

                    if (tagInfo.type == kTIFF_UndefinedType) continue;

                    const bool mapSingle = ((mapInfo.count == 1) || (mapInfo.type == kTIFF_ASCIIType));

                    if (mapSingle) {

                        if (!XMP_PropIsSimple(xmpForm)) continue;    // ? Notify client?

                        ExportSingleTIFF(tiff, ifd, mapInfo, nativeEndian, xmpValue);

                    }

                    else {

                        if (!XMP_PropIsArray(xmpForm)) continue;    // ? Notify client?

                        ExportArrayTIFF(tiff, ifd, mapInfo, nativeEndian, xmp, mapInfo.ns, mapInfo.name);

                    }

                }

            }

        } catch ( ... ) {

            // Do nothing, let other imports proceed.

            // ? Notify client?

        }

    }

}    // ExportTIFF_StandardMappings

也許是我對這套SDK還沒研究透徹，或許在設定tag子初已經有更為簡單有效的方式 ，總之我沒發現，暫且先這麼改完湊合用着吧。