[linux]基于libqrencode和libpng库的数据转为png格式的二维码图像的方法

一、需求

?按照数据生成png格式的二维码图片。

二、方案

整合libqrencode、libpng的两个方法，从而实现，详见文：

[linux]使用libqrencode库生成二维码数据https://evenurs.blog.csdn.net/article/details/135655176?spm=1001.2014.3001.5502[linux]使用libpng库将数据生成为png图像文件https://evenurs.blog.csdn.net/article/details/135667030?spm=1001.2014.3001.5502

三、源码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <png.h>
#include <qrencode.h>

void write_png_file(char* filename, int width, int height, png_bytep* row_pointers) {
    FILE* fp = fopen(filename, "wb");
    if (!fp) {
        printf("Error opening file %s for writing\n", filename);
        return;
    }

    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png_ptr) {
        printf("Error creating PNG write structure\n");
        fclose(fp);
        return;
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        printf("Error creating PNG info structure\n");
        png_destroy_write_struct(&png_ptr, NULL);
        fclose(fp);
        return;
    }

    if (setjmp(png_jmpbuf(png_ptr))) {
        printf("Error during PNG writing\n");
        png_destroy_write_struct(&png_ptr, &info_ptr);
        fclose(fp);
        return;
    }

    png_init_io(png_ptr, fp);

    png_set_IHDR(png_ptr, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGBA, PNG_INTERLACE_NONE,
                 PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

    png_write_info(png_ptr, info_ptr);

    png_write_image(png_ptr, row_pointers);

    png_write_end(png_ptr, NULL);

    png_destroy_write_struct(&png_ptr, &info_ptr);

    fclose(fp);
}

int QR_CreatePng(QRcode *res,char *fileName) {
    // int width = 256;
    // int height = 256;

    png_bytep* row_pointers = (png_bytep*)malloc(sizeof(png_bytep) * res->width);
    for (int y = 0; y < res->width; y++) {
        row_pointers[y] = (png_byte*)malloc(sizeof(png_byte) * res->width * 4);
        for (int x = 0; x < res->width; x++) {
            png_byte* pixel = &(row_pointers[y][x * 4]);
            if (res->data[y * res->width + x] & 0x01) {
                char pixBuf[4]={0,0,0,0xff};
                memcpy(pixel,pixBuf,4);
            } else {
                char pixBuf[4]={0xff,0xff,0xff,0xff};
                memcpy(pixel,pixBuf,4);
            }
        }
    }
    char buf[1024]={0};
    char*pngFile=".png";
    strcat(buf,fileName);
    strcat(buf,pngFile);
    printf("file name is %s\n",buf);
    write_png_file(buf, res->width, res->width, row_pointers);

    for (int y = 0; y < res->width; y++) {
        free(row_pointers[y]);
    }
    free(row_pointers);

    return 0;
}

QRcode *QR_CreateData(QRcode *qrcode,char*rawData){

    // unsigned char *data;
    int version = 1;
    // int width = 256;
    // int margin = 2;

    // 生成二维码数据
    qrcode = QRcode_encodeString(rawData, version, QR_ECLEVEL_L, QR_MODE_8, 1);
    if (qrcode == NULL) {
        fprintf(stderr, "Failed to encode string.\n");
        return NULL;
    }
    return qrcode;
}
int main(int argc, char **argv) {

	if (argc < 2)
	{

		printf("Usage:\n");
		printf("app argv[1] argv[2]\n");
		printf(" argv[1]: user data.\n");
		printf(" argv[2]: file name. \n");
		printf("for example:app www.abc.com abc \n");
		return -1;
	}

    QRcode *qrcode;
    QRcode *res=QR_CreateData(qrcode,argv[1]);
    if(res==NULL){
        goto exit;
    }else{
        QR_CreatePng(res,argv[2]);
        printf("data to %s.png finished.\n",argv[2]);
    }


exit:
    // 释放内存
    QRcode_free(qrcode);
    return 1;
}

四、gcc编译

Evenurs@admin-PowerEdge-S350-166:~/f1c100s/dev/f1c100s/tina$ /home/Evenurs/f1c100s/dev/f1c100s/tina/prebuilt/gcc/linux-x86/arm/toolchain-sunxi-arm9-musl/toolchain/bin/arm-openwrt-linux-muslgnueabi-gcc -I /home/Evenurs/f1c100s/dev/f1c100s/tina/out/c200s-F1C200s/compile_dir/target/libpng-1.2.56/ -I /home/Evenurs/f1c100s/dev/f1c100s/tina/out/c200s-F1C200s/compile_dir/target/zlib-1.2.8/ -I /home/Evenurs/f1c100s/dev/f1c100s/tina/out/c200s-F1C200s/compile_dir/target/qrencode-3.4.4/ data2png_app.c -o data2png_app -L /home/Evenurs/f1c100s/dev/f1c100s/tina/out/c200s-F1C200s/compile_dir/target/libpng-1.2.56/.libs/ -L /home/Evenurs/f1c100s/dev/f1c100s/tina/out/c200s-F1C200s/compile_dir/target/zlib-1.2.8/ -L /home/Evenurs/f1c100s/dev/f1c100s/tina/out/c200s-F1C200s/compile_dir/target/qrencode-3.4.4/.libs -lqrencode -lpng -lz
arm-openwrt-linux-muslgnueabi-gcc.bin: warning: environment variable 'STAGING_DIR' not defined
arm-openwrt-linux-muslgnueabi-gcc.bin: warning: environment variable 'STAGING_DIR' not defined
arm-openwrt-linux-muslgnueabi-gcc.bin: warning: environment variable 'STAGING_DIR' not defined

编译通过

五、通过adb push烧录

详细烧录步骤参考下文：

【adb】adb push命令 向设备传输文件https://evenurs.blog.csdn.net/article/details/128940198?spm=1001.2014.3001.5502

六、程序运行

root@TinaLinux:/# chmod -R 777 ./data2png_app
root@TinaLinux:/# ./data2png_app www.baidu.com baidu
file name is baidu.png
data to baidu.png finished.

?七、图片查看

八、扫码查看

九、结论

本文主要将前两天的方法进行了整合，如某些环节看不懂可参考前文，了解库函数作用即可编写本应用，接下来会实现图片尺寸的平铺效果。