Android平台生成二维码并实现扫描 & 识别功能

1.二维码的前世今生

“二维条码/二维码（2-dimensional bar code）是用某种特定的几何图形按一定规律在平面（二维方向上）分布的黑白相间的图形记录数据符号信息的；在代码编制上巧妙地利用构成计算机内部逻辑基础的“0”、“1”比特流的概念，使用若干个与二进制相对应的几何形体来表示文字数值信息，通过图象输入设备或光电扫描设备自动识读以实现信息自动处理：它具有条码技术的一些共性：每种码制有其特定的字符集；每个字符占有一定的宽度；具有一定的校验功能等。同时还具有对不同行的信息自动识别功能、及处理图形旋转变化点。 [1] ”

上面是百度百科的解释。既然有二维码，那么肯定有一维码。

一维码。最为常见的就是食品 & 书本后面的条码。

条码起源与20世纪40年代，后来在1970年 upc码发明，并开始广泛应用与食品包装。

具体的介绍可以看百度百科 一维码。

其实二维码与一维码本质上是类似的，就跟一维数组和二维数组一样。

2.二维码的java支持库

为了让java或者说android方便继承条码的功能，google就开发了一个zxing的库：

3.生成二维码

public class encodethread {
public static void encode(final string url, final int width, final int height, final encoderesult result) {
if (result == null) {
return;
}
if (textutils.isempty(url)) {
result.onencoderesult(null);
return;
}
new thread() {
@override
public void run() {
try {
multiformatwriter writer = new multiformatwriter();
hashtable<encodehinttype, string> hints = new hashtable<>();
hints.put(encodehinttype.character_set, "utf-8");
bitmatrix bitmatrix = writer.encode(url, barcodeformat.qr_code, width, height, hints);
bitmap bitmap = parsebitmatrix(bitmatrix);
result.onencoderesult(bitmap);
return;
} catch (writerexception e) {
e.printstacktrace();
}
result.onencoderesult(null);
}
}.start();
}
/**
* 生成二维码内容<br>
*
* @param matrix
* @return
*/
public static bitmap parsebitmatrix(bitmatrix matrix) {
final int qr_width = matrix.getwidth();
final int qr_height = matrix.getheight();
int[] pixels = new int[qr_width * qr_height];
//this we using qrcode algorithm
for (int y = 0; y < qr_height; y++) {
for (int x = 0; x < qr_width; x++) {
if (matrix.get(x, y)) {
pixels[y * qr_width + x] = 0xff000000;
} else {
pixels[y * qr_width + x] = 0xffffffff;
}
}
}
bitmap bitmap = bitmap.createbitmap(qr_width, qr_height, bitmap.config.argb_8888);
bitmap.setpixels(pixels, 0, qr_width, 0, 0, qr_width, qr_height);
return bitmap;
}
public interface encoderesult {
void onencoderesult(bitmap bitmap);
}
} 

zxing 支持很多条码格式：我们这里使用qr_code码。也就是我们常见的微信里面的二维码。

我们先来分析下这段代码：

multiformatwriter writer = new multiformatwriter();

这个是一个工具类，把所有支持的几个write写在里面了。

public bitmatrix encode(string contents,
barcodeformat format,
int width, int height,
map<encodehinttype,?> hints) throws writerexception {
writer writer;
switch (format) {
case ean_8:
writer = new ean8writer();
break;
case upc_e:
writer = new upcewriter();
break;
case ean_13:
writer = new ean13writer();
break;
case upc_a:
writer = new upcawriter();
break;
case qr_code:
writer = new qrcodewriter();
break;
case code_39:
writer = new code39writer();
break;
case code_93:
writer = new code93writer();
break;
case code_128:
writer = new code128writer();
break;
case itf:
writer = new itfwriter();
break;
case pdf_417:
writer = new pdf417writer();
break;
case codabar:
writer = new codabarwriter();
break;
case data_matrix:
writer = new datamatrixwriter();
break;
case aztec:
writer = new aztecwriter();
break;
default:
throw new illegalargumentexception("no encoder available for format " + format);
}
return writer.encode(contents, format, width, height, hints);
} 

这是官方最新支持的格式，具体看引入的jar里面支持的格式。

对与bitmatrix的结果，通过摸个算法，设置每个点白色，或者黑色。

最后创建一张二维码的图片。

4.识别二维码

如何从一张图片上面，识别二维码呢：

public class redecodethread {
public static void encode(final bitmap bitmap, final redecodethreadresult listener) {
if (listener == null) {
return;
}
if (bitmap == null) {
listener.onredecoderesult(null);
return;
}
new thread() {
@override
public void run() {
try {
multiformatreader multiformatreader = new multiformatreader();
bitmapluminancesource source = new bitmapluminancesource(bitmap);
binarybitmap bitmap1 = new binarybitmap(new hybridbinarizer(source));
result result1 = multiformatreader.decode(bitmap1);
listener.onredecoderesult(result1.gettext());
return;
} catch (notfoundexception e) {
e.printstacktrace();
}
listener.onredecoderesult(null);
}
}.start();
}
public interface redecodethreadresult {
void onredecoderesult(string url);
}
} 

过程也是很简单，使用multiformatreader来分析图片，这里不需要缺人图片的条码格式。

如果分析下源码，就是依次使用每种格式的reader来分析，直到找到合适的为止。

当然回了能够把bitmap转化成bitmatrix，然后在分析。

public final class bitmapluminancesource extends luminancesource{
private final byte[] luminances;
public bitmapluminancesource(string path) throws filenotfoundexception {
this(loadbitmap(path));
}
public bitmapluminancesource(bitmap bitmap) {
super(bitmap.getwidth(), bitmap.getheight());
int width = bitmap.getwidth();
int height = bitmap.getheight();
int[] pixels = new int[width * height];
bitmap.getpixels(pixels, 0, width, 0, 0, width, height);
// in order to measure pure decoding speed, we convert the entire image
// to a greyscale array
// up front, which is the same as the y channel of the
// yuvluminancesource in the real app.
luminances = new byte[width * height];
for (int y = 0; y < height; y++) {
int offset = y * width;
for (int x = 0; x < width; x++) {
int pixel = pixels[offset + x];
int r = (pixel >> 16) & 0xff;
int g = (pixel >> 8) & 0xff;
int b = pixel & 0xff;
if (r == g && g == b) {
// image is already greyscale, so pick any channel.
luminances[offset + x] = (byte) r;
} else {
// calculate luminance cheaply, favoring green.
luminances[offset + x] = (byte) ((r + g + g + b) >> 2);
}
}
}
}
@override
public byte[] getrow(int y, byte[] row) {
if (y < 0 || y >= getheight()) {
throw new illegalargumentexception("requested row is outside the image: " + y);
}
int width = getwidth();
if (row == null || row.length < width) {
row = new byte[width];
}
system.arraycopy(luminances, y * width, row, 0, width);
return row;
}
// since this class does not support cropping, the underlying byte array
// already contains
// exactly what the caller is asking for, so give it to them without a copy.
@override
public byte[] getmatrix() {
return luminances;
}
private static bitmap loadbitmap(string path) throws filenotfoundexception {
bitmap bitmap = bitmapfactory.decodefile(path);
if (bitmap == null) {
throw new filenotfoundexception("couldn't open " + path);
}
return bitmap;
}
} 

5.扫描二维码

扫描二维码，其实比上面只多了一步，就是把camera获取的东西直接转换，然后进行识别。

public void requestpreviewframe(handler handler, int message) {
if (camera != null && previewing) {
previewcallback.sethandler(handler, message);
if (useoneshotpreviewcallback) {
camera.setoneshotpreviewcallback(previewcallback);
} else {
camera.setpreviewcallback(previewcallback);
}
}
} 

首先把camera预览的数据放入previewcallback中。

final class previewcallback implements camera.previewcallback 

public void onpreviewframe(byte[] data, camera camera) {
point cameraresolution = configmanager.getcameraresolution();
if (!useoneshotpreviewcallback) {
camera.setpreviewcallback(null);
}
if (previewhandler != null) {
message message = previewhandler.obtainmessage(previewmessage, cameraresolution.x,
cameraresolution.y, data);
message.sendtotarget();
previewhandler = null;
} else {
log.d(tag, "got preview callback, but no handler for it");
}
} 

可以看到，预览的数据data，回传递过来，然后handler的方式传递出去。

接收data的地方：

@override
public void handlemessage(message message) {
switch (message.what) {
case r.id.decode:
//log.d(tag, "got decode message");
decode((byte[]) message.obj, message.arg1, message.arg2);
break;
case r.id.quit:
looper.mylooper().quit();
break;
}
} 

然后是decode data

private void decode(byte[] data, int width, int height) {
long start = system.currenttimemillis();
result rawresult = null;
//modify here
byte[] rotateddata = new byte[data.length];
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++)
rotateddata[x * height + height - y - 1] = data[x + y * width];
}
int tmp = width; // here we are swapping, that's the difference to #11
width = height;
height = tmp;
planaryuvluminancesource source = cameramanager.get().buildluminancesource(rotateddata, width, height);
binarybitmap bitmap = new binarybitmap(new hybridbinarizer(source));
try {
rawresult = multiformatreader.decodewithstate(bitmap);
} catch (readerexception re) {
// continue
} finally {
multiformatreader.reset();
}
if (rawresult != null) {
long end = system.currenttimemillis();
log.d(tag, "found barcode (" + (end - start) + " ms):\n" + rawresult.tostring());
message message = message.obtain(activity.gethandler(), r.id.decode_succeeded, rawresult);
bundle bundle = new bundle();
bundle.putparcelable(decodethread.barcode_bitmap, source.rendercroppedgreyscalebitmap());
message.setdata(bundle);
//log.d(tag, "sending decode succeeded message...");
message.sendtotarget();
} else {
message message = message.obtain(activity.gethandler(), r.id.decode_failed);
message.sendtotarget();
}
} 

当把camera上的图片转换成binarybitmap以后，剩下的事情，就更直接从图片识别是一样的。

planaryuvluminancesource source = cameramanager.get().buildluminancesource(rotateddata, width, height);
binarybitmap bitmap = new binarybitmap(new hybridbinarizer(source));