我无法复制png图片

Question

我尝试实现复制png图像指定区域的功能，但是“分段错误（核心已转储）”崩溃。检查是否超出数组的范围，仅绘制所选像素，一切正常。两点的坐标被输入到函数的输入端，沿着该点构建所需的区域。

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

#include <png.h>

#define FILE_NAME "spongebob.png"

struct png{

    int width, height;
    png_byte color_type;
    png_byte bit_depth;

    png_structp png_ptr;
    png_infop info_ptr;
    int number_of_passes;
    png_bytep *row_pointers;
};

void openPNG(struct png* image, char* fileName)
{

    int x,y;
    char heder[8];

    FILE *fp = fopen(fileName, "rb");

    if(!fp) printf("file is not opend\n");

    fread(heder, 1, 8, fp);

    image->png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);

    image->info_ptr = png_create_info_struct(image->png_ptr);


   png_init_io(image->png_ptr, fp);

   png_set_sig_bytes(image->png_ptr, 8);

    png_read_info(image->png_ptr, image->info_ptr);

    image->width = png_get_image_width(image->png_ptr, image->info_ptr);
    image->height = png_get_image_height(image->png_ptr, image->info_ptr);
    image->color_type = png_get_color_type(image->png_ptr, image->info_ptr);
    image->bit_depth = png_get_bit_depth(image->png_ptr, image->info_ptr);

    image->row_pointers = (png_bytep *) malloc(sizeof(png_bytep) * image->height);


    for (y = 0; y < image->height; y++)
        image->row_pointers[y] = (png_byte *) malloc(png_get_rowbytes(image->png_ptr, image->info_ptr));

    png_read_image(image->png_ptr, image->row_pointers);

    fclose(fp);
}

void doNewFile(struct png* image, char* fileName)
{

    int x, y;

    FILE *fp = fopen(fileName, "wb");

    if(!fp) printf("file is not open {doNewFile}\n");

    image->png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);


    image->info_ptr = png_create_info_struct(image->png_ptr);

    png_init_io(image->png_ptr, fp);

    png_set_IHDR(image->png_ptr, image->info_ptr, image->width, image->height,
                 image->bit_depth, image->color_type, PNG_INTERLACE_NONE,
                 PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

    png_write_info(image->png_ptr, image->info_ptr);

    png_write_image(image->png_ptr, image->row_pointers);

    png_write_end(image->png_ptr, NULL);

    for (y = 0; y < image->height; y++)
        free(image->row_pointers[y]);
    free(image->row_pointers);

    fclose(fp);

}



void doCopy(struct png *image, int Sx, int Sy, int Fx, int Fy)
{

    int x, y;
    int lenX = Fx - Sx + 1;
    int lenY = Fy - Sy + 1;

    printf("lenX = %d  lenY = %d\n", lenX, lenY);

    png_bytep *new_row_pointers =(png_bytep *) malloc(sizeof(png_bytep) * lenY); 

    for(y = 0; y < lenY; y++){
        new_row_pointers[y] = (png_byte *)malloc(sizeof(png_byte *) * lenX); 

        png_byte *torow = new_row_pointers[y]; 
        png_byte *row = image->row_pointers[Sy + y];

        for (x = 0; x < lenX; x++){


            png_byte *toptr = &(torow[x*4]); 
            png_byte *ptr = &(row[(Sx+x*4)]);


            toptr[0] = ptr[0];
            toptr[1] = ptr[1]; 
            toptr[2] = ptr[2];
            toptr[3] = ptr[3];

            /*ptr[0] = 0;
            ptr[1] = 255;      
            ptr[2] = 255;
            ptr[3] = 255;*/

            /*toptr[0] = 0;
            toptr[1] = 255;      
            toptr[2] = 255;   
            toptr[3] = 255;*/


        }
        image->row_pointers = new_row_pointers;  
        image->width = lenX; 
        image->height = lenY;

    }
}

int main(){

    int Sx = 100;
    int Sy = 100;

    int Fx = 2000;
    int Fy = 1000;


    struct png image;

    openPNG(&image, FILE_NAME);
    doCopy(&image, Sx , Sy, Fx, Fy);
    doNewFile(&image, "newFile.png");

}