# BarDecoder : Barcode and QR code decoder

The bardecoder module provides bar code decode function.

User can use the following code to import the bardecoder module.

var bardecoder = require('bardecoder');

# Support

The following shows bardecoder module APIs available for each permissions.

# BarDecoder Object

# bardecoder.defaultOpt([fast[, rotate[, format]]])

• fast {Boolean} Whether fast decode mode. default: false.
• rotate {Boolean} Whether try rotate image. default: false.
• format {String} Decoder format. default: undefined means auto recognition.
• Returns: {Object} Bar code decode options.

The returned object contains the following members:

• fast {Boolean} Whether fast decode mode.
• rotate {Boolean} Whether try rotate image.
• format {String} Decoder format.

format is a string, can be:

# bardecoder.decode(path[, opt])

• path {String} Image file path which need decode, suffix name can be *.png and *.jpg.
• opt {Object} Bar code decode option object. default: bardecoder.defaultOpt(false, false).
• Returns: {Object} Bar code decode result object.

The returned object contains the following members:

• text {String} Decode text.
• format {String} Decoder format.
• ecLevel {String} Error correction level.

# bardecoder.decode(buffer, subImageAttr[, opt])

• buffer {Buffer} Image buffer, image format can be RGB, YUV, Grayscale, JPEG, PNG.
• subImageAttr {Object} Bar code sub image attribute object, needed by image buffer.
• opt {Object} Bar code decode option object. default: bardecoder.defaultOpt(false, false).
• Returns: {Object} Bar code decode result object.

The returned object contains the following members:

• text {String} Decode text.
• format {String} Decoder format.
• ecLevel {String} Error correction level.

The bar code subImageAttr object contains the following members:

• left {Integer} Left position of bar code sub image in image buffer.
• top {Integer} Top position of bar code sub image in image buffer.
• width {Integer} Width of bar code sub image.
• height {Integer} Height of bar code sub image.
• pixelFormat {Integer} Pixel format.
• rowBytes {Integer} Row byte size of image buffer.
• pixelBytes {Integer} Pixel byte size of image buffer. Only RGB format needed.
• redIndex {Integer} Red index of RGB pixel. Only RGB format needed.
• greenIndex {Integer} Green index of RGB pixel. Only RGB format needed.
• blueIndex {Integer} Blue index of RGB pixel. Only RGB format needed.

pixelFormat is a integer, can be:

Bar code image is a sub image of image buffer, show as follow:

buf
 +-------------------------+
 |                         |
 | (left,top)              |
 |     +-------------+     |
 |     |             |     |
 |     |          height   |
 |     |             |     |
 |     +----width----+     |
 |                         |
 +---------rowBytes--------+

RGB pixel format:

For example RGBA8888:

    0       1       2       3
+-------+-------+-------+-------+
| red   | green |  blue | alpha |
+-------+-------+-------+-------+

pixelBytes is 4.
redIndex is 0.
greenIndex is 1.
blueIndex is 2.

For example RGB888:

    0       1       2 
+-------+-------+-------+
| red   | green |  blue | 
+-------+-------+-------+

pixelBytes is 3.
redIndex is 0.
greenIndex is 1.
blueIndex is 2.

# Example

This example show how to decode a PNG format QR Code image file.

var bardecoder = require('bardecoder');

var res = bardecoder.decode('./sylixos_qr.png');

// will print {text:www.sylixos.com,format:QR_CODE, ecLevel:L}
console.log(res);

This example show how to decode a PNG format Code-128 image file and use a decode option.

var bardecoder = require('bardecoder');

var opt = bardecoder.defaultOpt(true, false);

var res = bardecoder.decode('./sylixos_1d.png', opt);

// will print {text:www.sylixos.com,format:CODE_128,ecLevel:L}
console.log(res);

This example show how to decode a RGB888 format QR Code image buffer.

var res = bardecoder.decode(rgb888Buf, {
  left: 0, top: 0, width: 100, height: 100, rowBytes: 300, pixelBytes: 3, redIndex: 0, greenIndex: 1, blueIndex: 2, pixelFormat: bardecoder.PIX_FMT_RGB
});
console.log(res);

This example show how to decode a YUV format QR Code image buffer.

var res = bardecoder.decode(yuvBuf, {
  left: 0, top: 0, width: 100, height: 100, rowBytes: 100, pixelFormat: bardecoder.PIX_FMT_YUV420P
}); 
console.log(res);

This example show how to decode a Grayscale format QR Code image buffer.

var res = bardecoder.decode(grayscaleBuf, {
  left: 0, top: 0, width: 100, height: 100, rowBytes: 100, pixelFormat: bardecoder.PIX_FMT_GRAY8
}); 
console.log(res);

This example show how to decode a JPEG / MJPEG format QR Code image buffer.

var res = bardecoder.decode(jpegBuf, {
  pixelFormat: bardecoder.PIX_FMT_JPEG
}); 
console.log(res);

This example show how to decode a PNG format QR Code image buffer.

var res = bardecoder.decode(pngBuf, {
  pixelFormat: bardecoder.PIX_FMT_PNG
}); 
console.log(res);