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eValid -- Dynamic Image Validation Alternatives
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Image validation normally can be accomplished using existing Validation Modes, but not always.

A common situation is when the requirement is to validate an image for which there is limited or no advance knowledge on which to base the checkpoint.

Here are some suggestions and ideas for this situation:

  1. Image Synchronization
    The image synchronization logic requires advance (baseline) knowledge of a least a part of an image. eValid saves a checksum (not an image fragment). If possible, select the image from which the checksum is taken from an area that is known to be constant in advance.

  2. Watermark Check
    Many images have embedded watermark information that can be used to confirm image arrival. After completing synchronization with regular non-image-based methods, the script can include a SaveImage and SystemCall to a local Validate-Image-Function that PASSes or FAILs the saved image.

  3. Size Confirmation
    The script could use a SaveImage command and an offline function to validate image size.

  4. DOM Checking
    The DOM can be scanned at playback time in very great detail. See the DOM Element Manipulation commands for the kinds of actions that are possible. In some instances, in addition to the image proper, there are DOM values that are given particular values that signal complete arrival of an image, and this information can be used in achieving dynamic validation.

  5. DOM Property Extraction
    In some cases a varying image has the same or an approximately-the-same URL. The URL that populates an image can be found by reading the value for the IMG property in the DOM.

  6. Ultimate Limitation
    Ultimately, the non-determinism of an application may make it impossible to perform full or partial dynamic validation of image data.