Phonegap zbar prototype app

Phonegap zbar prototype app


Job Description

We would like to build a proof of concept prototype app that simply recreates the scanning functionality of the zbar app (zbar barcode plugin.)

Long 39 codes:

While it should be possible to read this symbol with the default settings, you may notice that it is not very reliable. You will have to stretch the symbol across the entire screen, and even then the default settings will only give you about 1.6 pixels per module, well below the ideal target of 3. To improve these results, we want to maximize scanning resolution for the long image axis.

Disable the default zoom/crop - zoom all the way out by hitting “Scan” and pinching the preview; the frame rate immediately drops to 8fps / 4.8fps.

We should compensate for this reduction in the frame rate:

Crop the image to a long, skinny rectangle - set the scanCrop setting to {{0, 0.3}, {1, 0.4}}; The frame rate jumps up to 18fps / 8.7fps.
Disable scans across the short image axis - set the CFG_X_DENSITY setting to 0. The frame rate goes all the way to 30fps / 13fps.

Since we have plenty of margin with the frame rate, we can minimize the total decode latency by performing more scan passes through the symbol:

Increase the scan density - set the CFG_Y_DENSITY setting to 1 (13.5fps / 5fps) or 2 (24fps / 9fps).

You should now be able to quickly and reliably decode long linear symbols.

If have an iPhone 4, you may also try increasing the resolution to support even longer symbols (NB there is no readertest setting for resolution). You may have to compensate elsewhere to bring the frame rate back to a reasonable level.

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