The TWAIN specification was developed by a consortium of industry companies. TWAIN devices generally comply fairly well to the TWAIN Specification however ambiguities in the specification were not fully resolved prior to vendors setting out to write drivers resulting in some difficulties between programs like Photoshop and some drivers. "Required" capabilities are not always functional. Units of measurement are sometimes confused.
TWAIN drivers are device specific.
Twain allows a digital imaging device to pass a picture to a computer augmented by additional information such as Author, Caption, Date, Time. The characteristics of the picture including resolution, pixel nature, image size, pixel depth, horizontal/vertical resolution, etc can be passed via TWAIN. TWAIN also distinguishes between default, preferred, and current device settings. 'Default settings' are those used after a reset. 'Preferred settings' are the optimal settings.
In addition to objective parameters, TWAIN also supports orientation, rotation, contrast, brightness, and shadow parameters that are substantially more subjective. Some difficulties may arise with these as example when a small number of device values must be mapped onto a wide range of potential values. e.g. should 4 brightness values be represented as 0 through 3? or -100, -333, +333, 1000? or something else?
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