Good Practices for Image Sample Uploads

event_note February 21, 2013

Of course the processing speed of the BioID Web Service (BWS) operations is mostly depending on our implementation. But you can follow some good practices on your side for accessing the BWS API.

Combine Sample Uploads

Instead of uploading one image after another each in separate API calls you should send a batch of images at once to speed up the enrollment. As you can see in the BioID Web Service SOAP API Documentation  the methods used for enrollment, verification, identification and quality check (you can use the BioID File Upload to give it a try) take an array of samples as parameter. This array can consist of several samples even of different traits. This prevents unnecessary header bytes from being sent.

Convert to Grayscale

The face trait doesn't use the color information of an image. You can see the samples on your profile page to see how the images are preprocessed before it is used for biometric template creation. So discarding the color information before sending the sample images should provide a decent size reduction of transferred data. And less data leads to less overall processing time.

Use Lossless Image Compression

We support images in the format BMP, GIF, TIFF, JPEG and PNG for upload to the BWS. Since compression of the image speeds up the transfer it is reasonable to do so. Although you can achieve higher compression using JPEG, we advise to use the lossless compression of PNG images. You could also use a tool like OptiPNG on the image before sending them.

Resolution and cropping

The uploaded images should have at least VGA resolution (640×480 pixels) with the face covering at least one quarter of the image area. However, note that sending huge images with several megapixels doesn't increase accuracy anymore (not all webcams are able to provide these resolutions anyway).

Please do not try to crop the images to the face area before uploading as you may crop too much thus reducing the accuracy of our algorithms or even preventing a face from being found.