/* The input argument is the source file pointer.
* The function returns an address to a dynamically allocated BMP_Image only
* if the file * contains a valid image file
* Otherwise, return NULL
* If the function cannot get the necessary memory to store the image, also
* return NULL
* Any error messages should be printed to stderr
*/
BMP_Image *Read_BMP_Image(FILE* fptr) {
BMP_Image *bmp_image = NULL;
int n;
//Allocate memory for BMP_Image*;
bmp_image = (BMP_Image *)malloc(sizeof(BMP_Image));
if(bmp_image == NULL)
{
fprintf(stderr, "Error allocating memory\n");
return NULL;
}
//Read the first 54 bytes of the source into the header
n = fread(&(bmp_image->header), sizeof(BMP_Header), 1, fptr);
// if read successful, check validity of header
if(n != 1)
{
fprintf(stderr, "Error reading input file\n");
return NULL;
}
if(!(Is_BMP_Header_Valid(&(bmp_image->header), fptr)))
{
fprintf(stderr, "Input file not in expected format\n");
return NULL;
}
// Allocate memory for image data
fseek(fptr, sizeof(BMP_Header), SEEK_SET);
bmp_image->data = (unsigned char*)malloc((bmp_image->header).imagesize * sizeof(unsigned char));
if(bmp_image->data == NULL)
{
fprintf(stderr, "Error allocating memory\n");
return NULL;
}
// read in the image data
n = fread(bmp_image->data, sizeof(unsigned char), (bmp_image->header).imagesize, fptr);
if(n != (bmp_image->header).imagesize)
{
fprintf(stderr, "Error reading input file\n");
return NULL;
}
return bmp_image;
}
BMP_Image *Read_BMP_Image(FILE* fptr) {
// go to the beginning of the file
BMP_Image *bmp_image = NULL;
fseek(fptr, 0, SEEK_SET);
//Allocate memory for BMP_Image*;
bmp_image = malloc(sizeof(*bmp_image));
if(bmp_image == NULL){
return NULL;
}
//Read the first 54 bytes of the source into the header
int status = fread(&(bmp_image -> header), 54, 1, fptr);
if(status != 1){
free(bmp_image);
return NULL;
}
// if read successful, check validity of header
if(!Is_BMP_Header_Valid(&(bmp_image -> header), fptr)){
free(bmp_image);
return NULL;
}
// Allocate memory for image data
bmp_image -> data = malloc(bmp_image -> header.imagesize);
if(bmp_image -> data == NULL){
free(bmp_image);
return NULL;
}
// read in the image data
fseek(fptr, 54, SEEK_SET);
status = fread(bmp_image -> data, bmp_image -> header.imagesize, 1, fptr);
if(status != 1){
free(bmp_image -> data);
free(bmp_image);
return NULL;
}
return bmp_image;
}
