error: invalid operands to binary *

How the heck am I getting this error?

error: invalid operands to binary *

Code:

---


*(yuv->y + i) = (0.257) * (image->data + (i*3)) +
                                                (0.504) * (image->data + (i*3+1)) +
                                                (0.098) * (image->data + (i*3+2)) + 16;
                                               
                *(yuv->u + i) = (0.439) * (image->data + (i*3)) +
                                                (0.368) * (image->data + (i*3+1)) -
                                                (0.071) * (image->data + (i*3+2)) + 128;
                                               
                *(yuv->v + i) =(-0.148) * (image->data + (i*3)) -
                                                (0.291) * (image->data + (i*3+1)) +
                                                (0.439) * (image->data + (i*3+2)) + 128;

---

I missed the dereference pointer *. But still one error. Thanks for viewing.

Code:

---


                *(yuv->y + i) = (0.257) * (*image->data + (i*3)) +
                                                (0.504) * (*image->data + (i*3+1)) +
                                                (0.098) * (*image->data + (i*3+2)) + 16;
                                               
                *(yuv->u + i) = (0.439) * (*image->data + (i*3)) +
                                                (0.368) * (*image->data + (i*3+1)) -
                                                (0.071) * (*image->data + (i*3+2)) + 128;
                                               
                *(yuv->v + i) =(-0.148) * (*image->data + (i*3)) -
                                                (0.291) * (*image->data + (i*3+1)) +
                                                (0.439) * (*image->data + (i*3+2)) + 128;

---

maybe some more context..
also if you are derefrence why are you still using -> ?
should it not be

(*image).data

Just to avoid confusion with C++ and OOP

if your data structs are like this :

Code:

---

struct test1
  {
  int    *data;
  };

struct test2
  {
  int  *y;
  int  *u;
  int  *v;
  };


struct test1 *image;
struct test2 *yuv;

---

Please don't try to run it like this.

Quote:

---

Originally Posted by cblix

I missed the dereference pointer *. But still one error. Thanks for viewing.

Code:

---


                *(yuv->y + i) = (0.257) * (*image->data + (i*3)) +
                                                (0.504) * (*image->data + (i*3+1)) +
                                                (0.098) * (*image->data + (i*3+2)) + 16;
                                               
                *(yuv->u + i) = (0.439) * (*image->data + (i*3)) +
                                                (0.368) * (*image->data + (i*3+1)) -
                                                (0.071) * (*image->data + (i*3+2)) + 128;
                                               
                *(yuv->v + i) =(-0.148) * (*image->data + (i*3)) -
                                                (0.291) * (*image->data + (i*3+1)) +
                                                (0.439) * (*image->data + (i*3+2)) + 128;

---

---

i hope u havn't clear under stood the structs with pointers concept. in many places u have used this

Code:

---

*image->data

---

the use of -> operator is b'cose of problem which we face at the operator precedence. let me explain u clear.

Code:

---

(*image.data)

---

looking at the code above u might guess that the code actually access the data members of the structure. but the fact is, it don't, but still looks like we are accessing it. the problem here is the * operator has more precedence than '.'. what we are actually expexting here to do is to get the data from the struct data member 'data' and dereferece to get the actual data out of it. thats was we are expecting.

in order to overcome this problem we starting useing -> operator which has more precedence than '.' and '*'. so it access it and derefereces it. having understood this u can now change your code to look soemthing as follow:

Code:

---

image->data

---

which look more meaning full now. ;)

ssharish2005