c - malloc 没有正确分配 3d 数组

Question

我正在用 c 编写一个程序，它将读取 ppm 输入文件并将其转换为 ASCII 艺术。在程序中，我分配了一个 3d 数组来存储输入文件的高度和宽度以及 RGB 组件。然后将数组元素(像素)转换为灰度并作为 ASCII 艺术写入输出文件。但是当我尝试编译以下代码时，编译器警告我:

asciiArt.c: In function 'main':

asciiArt.c:48:32 error: expected expression before 'int':

   array = malloc(width*sizeof(**int));
                                 ^           

asciiArt.c:50:35: error: expected expression before 'int':

  array[0] = malloc(height*sizeof(*int)); 
                                   ^  

但是第三个malloc()似乎是对的。为什么？谁能告诉我我做错了什么？

这是我的代码:

#include <stdio.h>
#include <stdlib.h>

char method_of_conversion(int greyscale){
    if(greyscale >= 230){
        return ' ';
    }else if(greyscale >= 200 && greyscale < 230){
        return '.';
    }else if(greyscale >= 180 && greyscale < 200){
        return '\'';
    }else if(greyscale >= 160 && greyscale < 180){
        return ':';
    }else if(greyscale >= 130 && greyscale < 160){
        return 'o';
    }else if(greyscale >= 100 && greyscale < 130){
        return '&';
    }else if(greyscale >= 70 && greyscale < 100){
        return '8';
    }else if(greyscale >= 50 && greyscale < 70){
        return '#';
    }else if(greyscale < 50){
        return '@';
    }
}

int main(){
    char ppmFile[100];
    char outputFile[100];

    int window_size;

    scanf("%s", &ppmFile); 
    scanf("%s", &outputFile); 
    // the size of a window of pixels to convert to ascii art character
    scanf("%d", &window_size); 

    FILE *input = fopen(ppmFile, "rb");
    FILE *output = fopen(outputFile, "w"); 


    char header[5]; //header = P6
    fscanf(input, "%s\n", header);
    int width, height, maxPixel; // max pixel is always 255
    // read the header from the ppm file
    fscanf(input, "%d %d %d\n", &width, &height, &maxPixel);

    int ***array;
    array = malloc(width*sizeof(**int));

    array[0] = malloc(height*sizeof(*int));

    array[0][0] = malloc(3*sizeof(int));


    int x, y;
    for (x = 0; x < width; x++){ 
        for(y=0; y < height; y++){
            array[x][y][0] = fgetc(input); //red
            array[x][y][1] = fgetc(input); //green
            array[x][y][2] = fgetc(input); //blue

            int greyscale;
            int i, j;
            for(i = 0; i < width; i+=window_size){
                for(j=0; j < height; j+=window_size){
                    // greyscale = (red + green +blue)/3;
                    greyscale = (array[x][y][0] + array[x][y][1] +array[x][y][2])/(3*window_size*window_size);
                    char c = method_of_conversion(greyscale);
                    fprintf(output,"%c",c); // write the ASCII art directly in the output file
                }
            }   
        }fprintf(output,"\n");
    }

    free(array);
    fclose(input);
    fclose(output);

    return 0;
}

Answer 1

你不能写 sizeof(*int) 你必须写 sizeof(int*)。

另请参阅 this answer查看如何更好地创建数组