Inverting the Values of a PPM image - c

Question

I am writing in C and I have to write code that will invert the RGB values for each pixel in an image. It's a simple process in that you take the max color value and subtract the actual RGB values. I have successfully read in the max color value, but when trying to invert the values, everything is returned as 0 and when written to a new file is not readable. Below is the code, any ideas?
Inverting the picture
int i,j;
for(i=0; i<myPic->rows;++i) {
//Moves up and down the columns reaching all Pixels
//Moves across left to right across all columns
for (j=0;j<myPic->cols;++j) {
//Inverstion requires the actual value to be subtracted from the max
myPic->pixels[i][j].red = myPic->colors - myPic->pixels[i][j].red;
myPic->pixels[i][j].green = myPic->colors - myPic->pixels[i][j].green;
myPic->pixels[i][j].blue = myPic->colors - myPic->pixels[i][j].blue;
}
}
return myPic;
}
Output of the image
fprintf(name,"P3\n%d %d\n%d\n",myPic->rows,myPic->cols,myPic->colors);
//The P3,rows,columns,and color values are all printed first
int i,j;
for(i=0; i< myPic->rows;++i) {
for(j=0; j<myPic->cols;++j) { //Each Pixel is printed one at a time
fprintf(name,"%d",myPic->pixels[i][j].red); //Red printed first
fprintf(name,"%d",myPic->pixels[i][j].green); //Green printed second
fprintf(name,"%d",myPic->pixels[i][j].blue); //Blue printed third
fprintf("\n");
}
}
}
Thanks for the help guys, this is what I'm using now and it works

Answer 1

When writing the pixel data, this line
myPic->pixels[i] = malloc(sizeof(Pixel) *myPic->cols);
overwrites the existing pointer, and makes it point to new (and more importantly, uninitialized) data.
Copy-paste programming (which you seem to have been doing) can work sometimes, but you have to take care to modify the copied code properly.
On an unrelated note, you don't print a newline after each line, so the resulting PPM file will actually not be correct.

Answer 2

#Joachim is correct. so do something like this:
int i,j;
for(i=0; i<myPic->rows;++i) {
Pixel[myPic->cols] temp = *myPic->pixels[i];
//Moves up and down the columns reaching all Pixels
myPic->pixels[i] = malloc(sizeof(Pixel) *myPic->cols);
//Moves across left to right across all columns
for (j=0;j<myPic->cols;++j) {
//Inverstion requires the actual value to be subtracted from the max
myPic->pixels[i][j].red = myPic->colors - temp[j].red;
myPic->pixels[i][j].green = myPic->colors - temp[j].green;
myPic->pixels[i][j].blue = myPic->colors - temp[j].blue;
}
}
return myPic;
}