Update dcmFileDraft.cpp
Update dcmFileDraft.cpp

Pre-allocate space for RAW frames to speed DCMfile creation

GoogleCloudPlatform/wsi-to-dicom-converter,GoogleCloudPlatform/wsi-to-dicom-converter,GoogleCloudPlatform/wsi-to-dicom-converter,GoogleCloudPlatform/wsi-to-dicom-converter