[技术]

【米尔MYS-8MMX开发板免费试用】使用libjpeg库和giflib库显示JPG图片和GIF图片

donatello1996

2021-8-30 21:13:26 2076 米尔开发板试用

0 Linux系统编程中对JPG和GIF图片的显示都有集成的软件库可以用，显示JPG图片可用libjpeg库，可以直接用apt在线安装 apt install libjpeg62-turbo libjpeg62-turbo-dev 对于ARM64架构的系统，会有turbo关键字，而在x86架构系统上面，直接安装libjpeg62即可。安装完毕之后，开发板的板上代码可以使用jpeglib.h提供的函数接口进行jpg文件的软件解码，直接读取jpg文件并显示在framebuffer外设之上，具体函数如下： -struct jpeg_decompress_struct cinfo; -用于存放JPG文件解码数据的结构体 -JSAMPARRAY buffer; -存放一行图像数据的结构体 -jpeg_create_decompress(&cinfo); -初始化jpeg_decompress结构体对象的函数 -jpeg_stdio_src(&cinfo,input_file); -指定解压缩数据源 void LCD_RGB888_Show_JPG_File(char dev , int xpos , int ypos , char filename) { //int fjpg; int i,j; FILE input_file = fopen(filename,"rb"); struct jpeg_decompress_struct cinfo; //JPEG图像在解码过程中 //使用jpeg_decompress_struct类型的结构体来表示 //图像的所有信息都存储在结构体中 struct jpeg_error_mgr jerr; //定义一个标准的错误结构体 JSAMPARRAY buffer; //用于存取一行数据 //fjpg = open((char )"/home/fa/1.jpg",O_RDONLY); cinfo.err = jpeg_std_error(&jerr); //绑定错误处理结构对象 jpeg_create_decompress(&cinfo); //初始化cinfo结构 jpeg_stdio_src(&cinfo,input_file); //指定解压缩数据源 jpeg_read_header(&cinfo,TRUE); //获取文件信息 jpeg_start_decompress(&cinfo); //开始解压缩 int width = cinfo.output_width; //图像宽度 int height = cinfo.output_height; //图像高度 int depth = cinfo.output_components; //图像深度 uint8_t img_byte = cinfo.jpeg_color_space; //像素字节数（1/2/3/4个字节，对应8/16/24/32位格式） memset(bmp_buf , 0 , sizeof(unsigned char) * width * height * depth); buffer = (cinfo.mem->alloc_sarray)((j_common_ptr)&cinfo,JPOOL_IMAGE , width depth , 1); //分配一行数据空间 point = bmp_buf; while(cinfo.output_scanline < height)//逐行读取位图数据 { jpeg_read_scanlines(&cinfo , buffer , 1); //读取一行jpg图像数据到buffer memcpy(point , buffer , width depth); //将buffer中的数据逐行给src_buff point += width * img_byte; //指针偏移一行 } jpeg_finish_decompress(&cinfo);//解压缩完毕 for(i = 0 ; i < LCD_HEIGHT ; i ++) { for(j = 0 ; j < LCD_WIDTH ; j ++) if(i <= height && j <= width) { uint32_t temp = bmp_buf[(i * width+j) * 3] << 16 \| bmp_buf[(i * width+j) * 3 + 1] << 8 \| bmp_buf[(i * width+j) * 3 + 2]; framebuffer_lcd[(i+ypos)(LCD_WIDTH)+j+xpos] = temp; } //else framebuffer_lcd[(i+ypos)(LCD_WIDTH)+j+xpos]=0; } int fd_lcd = open(dev , O_RDWR); write(fd_lcd , framebuffer_lcd , LCD_WIDTH * LCD_HEIGHT * 2); close(fd_lcd); } 复制代码值得注意的是，使用libjpeg函数要注意颜色位数，一般这个由板载的GPU芯片决定，具体可由以下函数获得GPU芯片的分辨率和显示颜色位数： void Get_Information_Frame_Buffer(char dev) { struct fb_var_screeninfo vinfo; printf("Open framebuffer device:%sn",dev); int fd_lcd = open(dev,O_RDWR); if(fd_lcd == -1) { printf("Open framebuffer device failed.n"); return ; } if (ioctl(fd_lcd,FBIOGET_VSCREENINFO,&vinfo)) { printf("Get framebuffer device info failedn"); return ; } close(fd_lcd); printf("%d %d %dn",vinfo.xres,vinfo.yres,vinfo.bits_per_pixel); } 复制代码* 如图，可以看出板上GPU显示位数为32位，那么就要用RGB888的buffer数据源进行显示。 JPG文件显示操作非常简单，接下来介绍一下稍微难一点的操作，显示GIF图片，显示GIF图片所用的giflib库无法从apt处在线安装，必须从指定网站获得源码： http://giflib.sourceforge.net/gif_lib.html 复制代码编译获得libgif.so.7.0.0，并做好两级软链接，由用户代码直接调用： libgif.zip (58.26 KB, 下载次数: 1 ) 运行时使用环境变量加载.so文件： export LD_LIBRARY_PATH=/home/proj 复制代码 LD_LIBRARY_PATH的路径为.so文件存在的路径，此export动作可以写到应用程序的启动脚本上，也可以手动执行。使用两个函数获得gif文件信息并循环显示： int GifLoadFile() { int error = 0; int size = 0; int idx = 0; int ret = 0; do { if (NULL == gEffectGifFile) { ret = -1; break; } gpGifFile = DGifOpenFileName(gEffectGifFile, &error); if (NULL == gpGifFile) { ret = -2; break; } if ((gpGifFile->SHeight == 0) \|\| (gpGifFile->SWidth == 0)) { ret = -3; break; } gpScreenBuffer = (GifRowType )malloc(gpGifFile->SHeight sizeof(GifRowType)); if (NULL == gpScreenBuffer) { ret = -4; break; } /* Size in bytes one row / size = gpGifFile->SWidth sizeof(GifPixelType); gpScreenBuffer[0] = (GifRowType)malloc(size); if(NULL == gpScreenBuffer[0]) { ret = -5; break; } /* Set its color to BackGround / for (idx = 0; idx < gpGifFile->SWidth; idx++) { gpScreenBuffer[0][idx] = gpGifFile->SBackGroundColor; } / Allocate the other rows, and set their color to background too / for (idx = 1; idx < gpGifFile->SHeight; idx++) { gpScreenBuffer[idx] = (GifRowType)malloc(size); if (NULL == gpScreenBuffer[idx]) { ret = -6; break; } memcpy(gpScreenBuffer[idx], gpScreenBuffer[0], size); } if (0 > ret) { break; } } while (0); if (0 > ret) { GifFreeFile(); } return ret; } void GifScreenBufferToRgb888(ColorMapObject ColorMap, uint8_t inRgb, GifRowType ScreenBuffer, int ScreenWidth, int ScreenHeight) { GifColorType ColorMapEntry = NULL; GifRowType GifRow = NULL; uint8_t rgbBuf = inRgb; int idxH = 0; int idxW = 0; for (idxH = 0; idxH < ScreenHeight; idxH++) { GifRow = ScreenBuffer[idxH]; rgbBuf = inRgb + idxH * ScreenWidth * 3; for (idxW = 0; idxW < ScreenWidth; idxW++) { ColorMapEntry = &ColorMap->Colors[GifRow[idxW]]; rgbBuf++ = ColorMapEntry->Red; rgbBuf++ = ColorMapEntry->Green; rgbBuf++ = ColorMapEntry->Blue; } } } int LCD_Show_Gif() { ColorMapObject colorMap = NULL; GifByteType extension = NULL; int InterlacedOffset[] = { 0, 4, 2, 1 }; // The way Interlaced image should int InterlacedJumps[] = { 8, 8, 4, 2 }; // be read - offsets and jumps... int extCode = 0; int row = 0; int col = 0; int width = 0; int height = 0; int iW = 0; int iH = 0; int ret = 0; do { if (DGifGetRecordType(gpGifFile, &gRecordType) == GIF_ERROR) { ret = -1; break; } switch (gRecordType) { case IMAGE_DESC_RECORD_TYPE: if (DGifGetImageDesc(gpGifFile) == GIF_ERROR) { ret = -2; break; } row = gpGifFile->Image.Top; col = gpGifFile->Image.Left; width = gpGifFile->Image.Width; height = gpGifFile->Image.Height; if (gpGifFile->Image.Interlace) { for (iH = 0; iH < 4; iH++) { for (iW = row + InterlacedOffset[iH]; iW < row + height; iW += InterlacedJumps[iH]) { DGifGetLine(gpGifFile, &gpScreenBuffer[iW][col], width); } } } else { for (iH = 0; iH < height; iH++) { DGifGetLine(gpGifFile, &gpScreenBuffer[row++][col], width); } } colorMap = (gpGifFile->Image.ColorMap ? gpGifFile->Image.ColorMap : gpGifFile->SColorMap); if (colorMap == NULL) { ret = -3; break; } GifScreenBufferToRgb888(colorMap, rgbBuf, gpScreenBuffer, gpGifFile->SWidth, gpGifFile->SHeight); LCD32_Show_Buffer8_Proportional_Stretch(FB_DEV , 0 , 0 , gpGifFile->SWidth , gpGifFile->SHeight , (unsigned char)rgbBuf , 3); break; case EXTENSION_RECORD_TYPE: /* Skip any extension blocks in file: / if (DGifGetExtension(gpGifFile, &extCode, &extension) == GIF_ERROR) { ret = -4; break; } while (extension != NULL) { if (DGifGetExtensionNext(gpGifFile, &extension) == GIF_ERROR) { ret = -5; break; } } break; case TERMINATE_RECORD_TYPE: break; default: break; } if (0 < ret) { break; } } while (gRecordType != TERMINATE_RECORD_TYPE); return ret; } 复制代码* 对libgif工具生成的buffer进行比例拉伸： int LCD32_Show_Buffer8_Proportional_Stretch(char dev_name , int xpos , int ypos , int width , int height ,unsigned char frame_buffer8[] , int multi) { int fd_lcd,i,j,count; fd_lcd = open(dev_name,O_RDWR); if(fd_lcd == -1) { printf("open LCD failed!n"); return -1; } for(i = 0 ; i < LCD_HEIGHT ; i++) { for(j = 0 ; j < LCD_WIDTH ; j++) { if(i <= height && j <= width) { if(multi == 2) { framebuffer_lcd[i LCD_WIDTH * multi + j * multi] = frame_buffer8[(i * width + j) * 3 ] << 16 \| frame_buffer8[(i * width + j) * 3 + 1] << 8 \| frame_buffer8[(i * width + j) * 3 + 2]; framebuffer_lcd[i * LCD_WIDTH * multi + j * multi + 1] = framebuffer_lcd[i * LCD_WIDTH * multi + j * multi]; framebuffer_lcd[i * LCD_WIDTH * multi + LCD_WIDTH + j * multi] = framebuffer_lcd[i * LCD_WIDTH * multi + j * multi]; framebuffer_lcd[i * LCD_WIDTH * multi + LCD_WIDTH + j * multi + 1] = framebuffer_lcd[i * LCD_WIDTH * multi + j * multi]; } else if(multi == 3) { framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos] = frame_buffer8[(i * width + j) * 3 ] << 16 \| frame_buffer8[(i * width + j) * 3 + 1] << 8 \| frame_buffer8[(i * width + j) * 3 + 2]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + 1 + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + 2 + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + LCD_WIDTH + j * multi + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + LCD_WIDTH + j * multi + 1 + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + LCD_WIDTH + j * multi + 2 + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + LCD_WIDTH * 2 + j * multi + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + LCD_WIDTH * 2 + j * multi + 1 + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + LCD_WIDTH * 2 + j * multi + 2 + xpos] = framebuffer_lcd[i * LCD_WIDTH * multi + ypos * LCD_WIDTH + j * multi + xpos]; } } } } write(fd_lcd,framebuffer_lcd,LCD_WIDTH * LCD_HEIGHT * 4); close(fd_lcd); return 0; } 复制代码演示视频稍后交由管理员上传。 0
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