二维码识别开源库-Quire码

QR码：
QR码是一种高密度矩阵条形码，而quirc是一个用于从图像中提取和解码它们的库。
它具有多种功能，因此非常适合此目的：
1、它足够快，可以用于实时视频：在现代x86内核上，从VGA帧提取和解码大约需要50毫秒
2、它具有鲁棒且宽容的识别算法。它可以正确识别和解码相机旋转和/或倾斜的QR码。它还可以区分和解码同一图像中的多个代码。
3、它易于使用，并且在单个带注释的头文件中描述了一个简单的API（有关概述，请参见下文）。
4、它很小，易于嵌入，除了标准C函数外没有任何依赖关系。
5、它的内存占用非常小：每个图像像素一个字节，每个解码器对象几个kB。
6、它不使用全局可变状态，并且可以在多线程应用程序中安全使用。
7、BSD许可，几乎没有关于使用和/或修改的限制。

库的使用：该库的所有功能都通过单个头文件公开，其中应包括：#include <quirc.h>要解码图像，您需要实例化一个struct quirc对象，这是通过quirc_new函数完成的。以后，当您不再需要解码任何内容时，应使用以下命令释放分配的内存quirc_destroy：struct quirc *qr;qr = quirc_new();if (!qr) {perror("Failed to allocate memory");abort();}/* ... */quirc_destroy(qr);获取解码器对象后，您需要设置将要使用的图像大小，可使用quirc_resize以下方法完成：if (quirc_resize(qr, 640, 480) < 0) {perror("Failed to allocate video memory");abort();}quirc_resize并且quirc_new是唯一的库函数，其分配内存。如果您打算处理一系列帧（或视频流），则可能要分配单个解码器并确定其大小，并保留该解码器以处理每个帧。处理框架分为两个阶段。第一阶段是称为识别的图像识别阶段，该阶段会拍摄灰度图像并搜索QR码。使用quirc_begin和quirc_end，您可以将灰度图像直接送入quirc用于图像处理的缓冲区中：uint8_t *image;int w, h;image = quirc_begin(qr, &w, &h);/* Fill out the image buffer here.* image is a pointer to a w*h bytes.* One byte per pixel, w pixels per line, h lines in the buffer.*/quirc_end(qr);注意，quirc_begin仅返回指向先前分配的缓冲区的指针。缓冲区将包含未初始化的数据。呼叫至后quirc_end，解码器会保存一个可通过quirc_count和查询的QR码列表quirc_extract。此时，处理的第二阶段发生-解码。这是通过调用来完成的，该调用quirc_decode与解码器对象无关。int num_codes;int i;/* We've previously fed an image to the decoder via* quirc_begin/quirc_end.*/num_codes = quirc_count(qr);for (i = 0; i < num_codes; i++) {struct quirc_code code;struct quirc_data data;quirc_decode_error_t err;quirc_extract(qr, i, &code);/* Decoding stage */err = quirc_decode(&code, &data);if (err)printf("DECODE FAILED: %s\n", quirc_strerror(err));elseprintf("Data: %s\n", data.payload);}quirc_code并且quirc_data是扁平结构，使用后无需初始化或释放。     版权所有（C）2010-2012 Daniel Beer < dlbeer@gmail.com >

quirc.文件

#ifndef QUIRC_H_
#define QUIRC_H_#include <stdint.h>#ifdef __cplusplus
extern "C" {
#endifstruct quirc;/* Obtain the library version string. */
const char *quirc_version(void);/* Construct a new QR-code recognizer. This function will return NULL* if sufficient memory could not be allocated.*/
struct quirc *quirc_new(void);/* Destroy a QR-code recognizer. */
void quirc_destroy(struct quirc *q);/* Resize the QR-code recognizer. The size of an image must be* specified before codes can be analyzed.** This function returns 0 on success, or -1 if sufficient memory could* not be allocated.*/
int quirc_resize(struct quirc *q, int w, int h);/* These functions are used to process images for QR-code recognition.* quirc_begin() must first be called to obtain access to a buffer into* which the input image should be placed. Optionally, the current* width and height may be returned.** After filling the buffer, quirc_end() should be called to process* the image for QR-code recognition. The locations and content of each* code may be obtained using accessor functions described below.*/
uint8_t *quirc_begin(struct quirc *q, int *w, int *h);
void quirc_end(struct quirc *q);/* This structure describes a location in the input image buffer. */
struct quirc_point {int x;int   y;
};/* This enum describes the various decoder errors which may occur. */
typedef enum {QUIRC_SUCCESS = 0,QUIRC_ERROR_INVALID_GRID_SIZE,QUIRC_ERROR_INVALID_VERSION,QUIRC_ERROR_FORMAT_ECC,QUIRC_ERROR_DATA_ECC,QUIRC_ERROR_UNKNOWN_DATA_TYPE,QUIRC_ERROR_DATA_OVERFLOW,QUIRC_ERROR_DATA_UNDERFLOW
} quirc_decode_error_t;/* Return a string error message for an error code. */
const char *quirc_strerror(quirc_decode_error_t err);/* Limits on the maximum size of QR-codes and their content. */
#define QUIRC_MAX_BITMAP    3917
#define QUIRC_MAX_PAYLOAD   8896/* QR-code ECC types. */
#define QUIRC_ECC_LEVEL_M     0
#define QUIRC_ECC_LEVEL_L     1
#define QUIRC_ECC_LEVEL_H     2
#define QUIRC_ECC_LEVEL_Q     3/* QR-code data types. */
#define QUIRC_DATA_TYPE_NUMERIC       1
#define QUIRC_DATA_TYPE_ALPHA         2
#define QUIRC_DATA_TYPE_BYTE          4
#define QUIRC_DATA_TYPE_KANJI         8/* Common character encodings */
#define QUIRC_ECI_ISO_8859_1        1
#define QUIRC_ECI_IBM437        2
#define QUIRC_ECI_ISO_8859_2        4
#define QUIRC_ECI_ISO_8859_3        5
#define QUIRC_ECI_ISO_8859_4        6
#define QUIRC_ECI_ISO_8859_5        7
#define QUIRC_ECI_ISO_8859_6        8
#define QUIRC_ECI_ISO_8859_7        9
#define QUIRC_ECI_ISO_8859_8        10
#define QUIRC_ECI_ISO_8859_9        11
#define QUIRC_ECI_WINDOWS_874       13
#define QUIRC_ECI_ISO_8859_13       15
#define QUIRC_ECI_ISO_8859_15       17
#define QUIRC_ECI_SHIFT_JIS     20
#define QUIRC_ECI_UTF_8         26/* This structure is used to return information about detected QR codes* in the input image.*/
struct quirc_code {/* The four corners of the QR-code, from top left, clockwise */struct quirc_point    corners[4];/* The number of cells across in the QR-code. The cell bitmap* is a bitmask giving the actual values of cells. If the cell* at (x, y) is black, then the following bit is set:**     cell_bitmap[i >> 3] & (1 << (i & 7))** where i = (y * size) + x.*/int         size;uint8_t            cell_bitmap[QUIRC_MAX_BITMAP];
};/* This structure holds the decoded QR-code data */
struct quirc_data {/* Various parameters of the QR-code. These can mostly be* ignored if you only care about the data.*/int         version;int         ecc_level;int           mask;/* This field is the highest-valued data type found in the QR* code.*/
int         data_type;/* Data payload. For the Kanji datatype, payload is encoded as* Shift-JIS. For all other datatypes, payload is ASCII text.*/
uint8_t         payload[QUIRC_MAX_PAYLOAD];
int         payload_len;
/* ECI assignment number */
uint32_t        eci;
};
/* Return the number of QR-codes identified in the last processed* image.* */* int quirc_count(const struct quirc *q);* /* Extract the QR-code specified by the given index. */* void quirc_extract(const struct quirc *q, int index,struct quirc_code *code);/* Decode a QR-code, returning the payload data. */quirc_decode_error_t quirc_decode(const struct quirc_code *code,struct quirc_data *data);#ifdef __cplusplus}#endif#endif

quirc.c文件

#include <stdlib.h>
#include <string.h>
#include "quirc_internal.h"const char *quirc_version(void)
{return "1.0";
}struct quirc *quirc_new(void)
{struct quirc *q = malloc(sizeof(*q));if (!q)return NULL;memset(q, 0, sizeof(*q));return q;
}void quirc_destroy(struct quirc *q)
{free(q->image);/* q->pixels may alias q->image when their type representation is of thesame size, so we need to be careful here to avoid a double free */if (!QUIRC_PIXEL_ALIAS_IMAGE)free(q->pixels);free(q);
}int quirc_resize(struct quirc *q, int w, int h)
{uint8_t        *image  = NULL;quirc_pixel_t   *pixels = NULL;/** XXX: w and h should be size_t (or at least unsigned) as negatives* values would not make much sense. The downside is that it would break* both the API and ABI. Thus, at the moment, let's just do a sanity* check.*/if (w < 0 || h < 0)goto fail;/** alloc a new buffer for q->image. We avoid realloc(3) because we want* on failure to be leave `q` in a consistant, unmodified state.*/image = calloc(w, h);if (!image)goto fail;/* compute the "old" (i.e. currently allocated) and the "new"(i.e. requested) image dimensions */size_t olddim = q->w * q->h;size_t newdim = w * h;size_t min = (olddim < newdim ? olddim : newdim);/** copy the data into the new buffer, avoiding (a) to read beyond the* old buffer when the new size is greater and (b) to write beyond the* new buffer when the new size is smaller, hence the min computation.*/(void)memcpy(image, q->image, min);/* alloc a new buffer for q->pixels if needed */if (!QUIRC_PIXEL_ALIAS_IMAGE) {pixels = calloc(newdim, sizeof(quirc_pixel_t));if (!pixels)goto fail;}/* alloc succeeded, update `q` with the new size and buffers */q->w = w;q->h = h;free(q->image);q->image = image;if (!QUIRC_PIXEL_ALIAS_IMAGE) {free(q->pixels);q->pixels = pixels;}return 0;/* NOTREACHED */
fail:free(image);free(pixels);return -1;
}int quirc_count(const struct quirc *q)
{return q->num_grids;
}static const char *const error_table[] = {[QUIRC_SUCCESS] = "Success",[QUIRC_ERROR_INVALID_GRID_SIZE] = "Invalid grid size",[QUIRC_ERROR_INVALID_VERSION] = "Invalid version",[QUIRC_ERROR_FORMAT_ECC] = "Format data ECC failure",[QUIRC_ERROR_DATA_ECC] = "ECC failure",[QUIRC_ERROR_UNKNOWN_DATA_TYPE] = "Unknown data type",[QUIRC_ERROR_DATA_OVERFLOW] = "Data overflow",[QUIRC_ERROR_DATA_UNDERFLOW] = "Data underflow"
};const char *quirc_strerror(quirc_decode_error_t err)
{if (err >= 0 && err < sizeof(error_table) / sizeof(error_table[0]))return error_table[err];return "Unknown error";
}

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