读取PPM文件并将其存储在数组中;用C编码

2 回答

• 3

  以下代码显示如何读取，更改像素颜色以及以PPM格式写入图像 . 我希望它有所帮助 .

  #include<stdio.h>
  #include<stdlib.h>
  
  typedef struct {
       unsigned char red,green,blue;
  } PPMPixel;
  
  typedef struct {
       int x, y;
       PPMPixel *data;
  } PPMImage;
  
  #define CREATOR "RPFELGUEIRAS"
  #define RGB_COMPONENT_COLOR 255
  
  static PPMImage *readPPM(const char *filename)
  {
           char buff[16];
           PPMImage *img;
           FILE *fp;
           int c, rgb_comp_color;
           //open PPM file for reading
           fp = fopen(filename, "rb");
           if (!fp) {
                fprintf(stderr, "Unable to open file '%s'\n", filename);
                exit(1);
           }
  
           //read image format
           if (!fgets(buff, sizeof(buff), fp)) {
                perror(filename);
                exit(1);
           }
  
      //check the image format
      if (buff[0] != 'P' || buff[1] != '6') {
           fprintf(stderr, "Invalid image format (must be 'P6')\n");
           exit(1);
      }
  
      //alloc memory form image
      img = (PPMImage *)malloc(sizeof(PPMImage));
      if (!img) {
           fprintf(stderr, "Unable to allocate memory\n");
           exit(1);
      }
  
      //check for comments
      c = getc(fp);
      while (c == '#') {
      while (getc(fp) != '\n') ;
           c = getc(fp);
      }
  
      ungetc(c, fp);
      //read image size information
      if (fscanf(fp, "%d %d", &img->x, &img->y) != 2) {
           fprintf(stderr, "Invalid image size (error loading '%s')\n", filename);
           exit(1);
      }
  
      //read rgb component
      if (fscanf(fp, "%d", &rgb_comp_color) != 1) {
           fprintf(stderr, "Invalid rgb component (error loading '%s')\n", filename);
           exit(1);
      }
  
      //check rgb component depth
      if (rgb_comp_color!= RGB_COMPONENT_COLOR) {
           fprintf(stderr, "'%s' does not have 8-bits components\n", filename);
           exit(1);
      }
  
      while (fgetc(fp) != '\n') ;
      //memory allocation for pixel data
      img->data = (PPMPixel*)malloc(img->x * img->y * sizeof(PPMPixel));
  
      if (!img) {
           fprintf(stderr, "Unable to allocate memory\n");
           exit(1);
      }
  
      //read pixel data from file
      if (fread(img->data, 3 * img->x, img->y, fp) != img->y) {
           fprintf(stderr, "Error loading image '%s'\n", filename);
           exit(1);
      }
  
      fclose(fp);
      return img;
  }
  void writePPM(const char *filename, PPMImage *img)
  {
      FILE *fp;
      //open file for output
      fp = fopen(filename, "wb");
      if (!fp) {
           fprintf(stderr, "Unable to open file '%s'\n", filename);
           exit(1);
      }
  
      //write the header file
      //image format
      fprintf(fp, "P6\n");
  
      //comments
      fprintf(fp, "# Created by %s\n",CREATOR);
  
      //image size
      fprintf(fp, "%d %d\n",img->x,img->y);
  
      // rgb component depth
      fprintf(fp, "%d\n",RGB_COMPONENT_COLOR);
  
      // pixel data
      fwrite(img->data, 3 * img->x, img->y, fp);
      fclose(fp);
  }
  
  void changeColorPPM(PPMImage *img)
  {
      int i;
      if(img){
  
           for(i=0;i<img->x*img->y;i++){
                img->data[i].red=RGB_COMPONENT_COLOR-img->data[i].red;
                img->data[i].green=RGB_COMPONENT_COLOR-img->data[i].green;
                img->data[i].blue=RGB_COMPONENT_COLOR-img->data[i].blue;
           }
      }
  }
  
  int main(){
      PPMImage *image;
      image = readPPM("can_bottom.ppm");
      changeColorPPM(image);
      writePPM("can_bottom2.ppm",image);
      printf("Press any key...");
      getchar();
  }
  

  回复于 2024-04-30T15:33:30+08:00
• 20

  这是PPM specification .

  PPM文件由9个部分构成，用空格分隔 .

  • 打开文件

  • 读到第一个空格并检查 P6 . 然后跳过其他白色空格 .

  • 读到下一个空格，将缓冲区转换为整数宽度 . 然后跳过其他白色空格

  • 读到下一个空格，将缓冲区转换为整数高度 . 然后跳过其他白色空格

  • 分配高度*宽度大小的二维整数数组

  • 读取max-val

  • 逐行读取并填充数组

  回复于 2024-04-30T15:33:30+08:00