我是C程序的初学者。我正在尝试编写一个程序，该程序读取BMP文件并写入Image文件的副本。但是，当我以较小的代码执行此代码时，它会进行1次迭代，然后显示Null指针分配。请帮我解决这个问题
我正在Turbo C / Windows 7 OS中运行此代码
#define MAX_FILE_NAME_SIZE 100
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<conio.h>
struct Pixel
{
unsigned char red;
unsigned char green;
unsigned char blue;
};
struct RGB_Image
{
char file_name[MAX_FILE_NAME_SIZE];
long height;
long width;
long size;
struct Pixel** pixels;
};
//following functions are used for loading and saving of images
int load_image(struct RGB_Image* image);
int save_image(struct RGB_Image image) ;
/// following function is used free up allcated memories for pixels
void free_pixels(struct RGB_Image image);
// following function is used for re allocate memories for pixels
void re_allocate_pixels(struct RGB_Image* image, int new_height, int new_width);
// following functin are used to manipulate images like
// removing channel, inerting image, quantire image, flip images, etc
void save_copy_image();
void remove_channel_image();
void invert_image();
void quantize_image();
void flip_hrizontal_image();
void change_luminonsity_image();
void print_information_image();
void crop_image();
void change_luminosity();
// following functions are used to manipulate pixels of image
// like invert pixels, flip images, remove pixels, etc
void invert_pixels(struct Pixel** pixels, int height, int width);
void flip_hrizntal_pixels(struct Pixel** pixels, int height, int width);
void quantize_pixels(struct Pixel** pixels, int height, int width, int quantize_level);
void remove_red_pixels(struct Pixel** pixels, int height, int width);
void remove_green_pixels(struct Pixel** pixels, int height, int width);
void remove_blue_pixels(struct Pixel** pixels, int height, int width);
void change_luminosity_pixels(struct Pixel** pixels, int height, int width, int luminosity_level);
void free_pixels(struct RGB_Image image)
{
long i=0;
for(;i<image.height;i++)
{
free(image.pixels[i]);
}
}
void print_information_image()
{
struct RGB_Image image;
int file_status;
file_status = load_image(&image);
if(file_status == 0)
{
printf("File name : %s\n", image.file_name);
printf("Height : %ld\n", image.height);
printf("Width : %ld\n", image.width);
printf("Size : %ld\n", image.size);
free_pixels(image);
}
}
// loads image to passed pointer variable
int load_image(struct RGB_Image* image_pointer)
{
// decalre variable for storing file name
char file_name[MAX_FILE_NAME_SIZE];
// decalre file pointer
FILE *file_pointer;
long i,j;
//long k=0;
// read file name and store it in image pointer
printf("\n Enter the file name : ");
scanf("%s", image_pointer->file_name);
// copy file name from pointer to local variables
strcpy(file_name, image_pointer->file_name);
// append bmp extension
strcat(file_name, ".bmp");
// read a file
file_pointer = fopen(file_name, "rb");
// if there is an error, return 1
if(file_pointer == NULL)
{
printf("\n File can not be opened");
return 1;
}
// move the opened file and move 2 bytes
fseek(file_pointer, 2, SEEK_SET);
// read the size of file
fread(&(image_pointer->size), 4, 1, file_pointer);
// move 12 bytes further
fseek(file_pointer, 12, SEEK_CUR);
// read height and width of file
fread(&(image_pointer->width), 4, 1, file_pointer);
fread(&(image_pointer->height), 4, 1, file_pointer);
// move 28 bytes for reading further content
fseek(file_pointer, 28, SEEK_CUR);
// printf("dim read finished\n");
// assign pointers for each row
image_pointer->pixels = (struct Pixel**) malloc(sizeof(*image_pointer->pixels) * image_pointer->height);
// printf("craete first pointers finished\n");
i = 0;
for(;i<image_pointer->height;i++)
{
image_pointer->pixels[i] = (struct Pixel*) malloc(sizeof(struct Pixel*) * image_pointer->width);
}
// printf("create indiv pointers finished\n");
for(i=0;i<image_pointer->height;i++)
{
for(j=0;j<image_pointer->width;j++)
{
fread(&(image_pointer->pixels[i][j].red), 1, 1, file_pointer);
fread(&(image_pointer->pixels[i][j].green), 1, 1, file_pointer);
fread(&(image_pointer->pixels[i][j].blue), 1, 1, file_pointer);
//k += 3;
}
}
//printf("file is copied \n");
// printf("total value %ld", k);
fclose(file_pointer);
printf("\n Image loaded \n \n");
return 0;
}
void save_copy_image()
{
struct RGB_Image image;
int file_status = load_image(&image);
if (file_status == 0) {
strcat(image.file_name, "_copy");
printf("\nImage Copied");
save_image(image);
free_pixels(image);
}
}
int save_image(struct RGB_Image image) {
long i, j;
char copy_file_name[MAX_FILE_NAME_SIZE];
FILE *file_pointer;
int image_datasize = image.size - 40;
unsigned char bmp_header[54] = {
0x42, 0x4D, 0, 0, 0, 0,
0X00,0X00,0X00,0X00,
0x36,0x00,0x00,0x00,
0x28,0x00,0x00,0x00,
0, 0, 0, 0,
0, 0, 0, 0,
0x01,0x00,0x18,0x00,
0x00,0x00,0x00,0x00,
0, 0, 0, 0,
0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,
0X00,0X00,0X00,0X00
};
bmp_header[2] = image.size;
bmp_header[3] = image.size >> 8;
bmp_header[4] = image.size >> 16;
bmp_header[5] = image.size >> 24;
bmp_header[18] = image.width;
bmp_header[19] = image.width >> 8;
bmp_header[20] = image.width >> 16;
bmp_header[21] = image.width >> 24;
bmp_header[22] = image.height;
bmp_header[23] = image.height >> 8;
bmp_header[24] = image.height >> 16;
bmp_header[25] = image.height >> 24;
bmp_header[34] = image_datasize;
bmp_header[35] = image_datasize >> 8;
bmp_header[36] = image_datasize >> 16;
bmp_header[37] = image_datasize >> 24;
strcpy(copy_file_name, image.file_name);
strcat(copy_file_name, ".bmp");
file_pointer = fopen(copy_file_name, "wb");
if (file_pointer == NULL) {
printf("\nFile can not be opened.");
return 1;
}
fwrite(bmp_header, 1, 54, file_pointer);
for (i=0;i < image.height;i++) {
for (j=0;j < image.width;j++) {
fwrite(&(image.pixels[i][j].red), 1, 1, file_pointer);
fwrite(&(image.pixels[i][j].green), 1, 1, file_pointer);
fwrite(&(image.pixels[i][j].blue), 1, 1, file_pointer);
}
}
fclose(file_pointer);
printf("\nImage Saved %d", image_datasize);
return 0;
}
void change_luminosity_pixels(struct Pixel** pixels, int height, int width, int luminosity_level)
{
int i, j, value_red = 0, value_green = 0, value_blue = 0;
for (i=0;i < height;i++) {
for (j=0;j < width;j++) {
value_red = pixels[i][j].red + luminosity_level;
if(value_red > 255)
value_red = 255;
else if(value_red < 0)
value_red = 0;
printf("red value = %d", value_red);
pixels[i][j].red = value_red;
//fwrite(&(value_red), 1, 1, file_pointer);
value_green = pixels[i][j].green + luminosity_level;
if(value_green > 255)
value_green = 255;
else if(value_green < 0)
value_green = 0;
printf("green value = %d", value_green);
pixels[i][j].green = value_green;
//fwrite(&(value_green), 1, 1, file_pointer);
value_blue = pixels[i][j].blue + luminosity_level;
if(value_blue > 255)
value_blue = 255;
else if(value_blue < 0)
value_blue = 0;
printf("blue value = %d", value_blue);
pixels[i][j].blue = value_blue;
//fwrite(&(value_blue), 1, 1, file_pointer);
}
}
}
void change_luminosity()
{
struct RGB_Image image;
int luminosity_level, file_status;
file_status = load_image(&image);
if(file_status == 0)
{
printf(" Enter the luminosity: ");
scanf("%d", &luminosity_level);
change_luminosity_pixels(image.pixels, image.height, image.width, luminosity_level);
strcat(image.file_name, "_luminosity_");
//strcat(image.file_name, luminosity_level);
save_image(image);
printf("Image luminosity changed by a level of %d", luminosity_level);
free_pixels(image);
}
}
// starts main program
int main()
{
int choice = -2;
clrscr();
while(choice != -1)
{
printf("\n\n IMAGE MENU\n");
printf("0. Print Image Information\n");
printf("1. Save Copy of Image\n");
printf("2. Change Luminosity\n");
printf("3. Remove Image Channel\n");
printf("4. Invert Image Clours\n");
printf("5. Quantize Image\n");
printf("6. Flip Image Horizntally\n");
printf("7. Crop Image\n");
printf("-1. Quit\n");
printf("Enter your choice : ");
scanf("%d", &choice);
switch(choice)
{
case 0:
print_information_image();
break;
case 1:
save_copy_image();
break;
case 2:
break;
case 3:
break;
case 4:
break;
case 5:
break;
case 6:
break;
case 7:
break;
case -1:
exit(0);
break;
default:
//continue;
break;
}
}
printf("\\ Test");
getch();
return 0;
}
它应该可以处理所有大小的bmp文件>请帮帮我