Prepare your samples!
We have some recommendation about the characteristics of image data. The BWS does an quality check on all image data sent to the service. Only if the check succeeds the sample is processed further.
One important parameter is the size of the image. Keep in mind that the upload from your developer workstation with a good network connection is several times faster than an upload from an mobile device over a cellular network.
The processing of the data needs only a fraction of the time the data transfer to and from the BWS consumes. So the key to a good customer experience is the reduction of data without reducing the information the biometric operation of the BWS needs from the image.
It's a good practice to discard the color information.
Converting the images to gray scale usually cuts down the size to one third of the original amount of data without losing quality concerning biometrics. The color information - if present - is removed by the BWS anyway.
The aspect ratio of the image should be 3:4 so size can be reduced also by cropping the image to that ratio.
But be sure not to crop the head of the person you want to process with the BioID Web Service.
You can reduce the image size down to an height of 480 pixels for an enrollment operation and to an image height of at least 320 pixels for the verification operation to reduce the data further.
The face of the person should cover most parts of the image at such low resolutions.
By discarding color information, cropping the image and reducing the size combined with an loss less compression algorithm you can vastly improve the overall processing speed of BWS operations.
This is one important building block of your application for more customer satisfaction!