Dali: VectorImage -- C API

Header Files

#include <dvmbasic.h>

Type Definitions

Vector

A Vector represents a motion vector, (e.g., in a MPEG video). It has x and y components, and a flag to indicate if the vector exists. (The exists flags can be used for other purposes as the programmer sees fit.)

    typedef struct Vector {
        char exists;
        char down;
        char right;
    } Vector;

exists

0 if the vector is not initialized. 1 if the down and right are initialized. 2 if the vector is skipped (in MPEG B-frame encoding only).

down

Down vector component

right

Right vector component

VectorImage

A VectorImage is a buffer storing 2D array of Vector. Just like a ByteImage, a VectorImage can be either physical or virtual.

    typedef struct VectorImage {
        int width;
        int height;
        int x;
        int y;
        int parentWidth;
        unsigned char isVirtual;
        Vector *firstVector;
    } VectorImage;

width

the width of the VectorImage

height

the height of the VectorImage

x

the x-offset of the top-left corner of the VectorImage from it's parent.

y

the y-offset of the top-left corner of the VectorImage from it's parent.

parentWidth

the width of the physical parent of this VectorImage. (should be called rootWidth since the parent might not be physical)

virtual

1 iff the VectorImage is virtual. 0 otherwise.

firstVector

pointer to the first vector in this VectorImage.

Constants

Return Codes

Return codes from various vector primitives. DVM_VECTOR_OK indicates the primitives executed successfully. DVM_VECTOR_ERROR indicates some error has occurs. We may defined more error codes to indicates different type of errors.

    #define DVM_VECTOR_OK 0
    #define DVM_VECTOR_ERROR 1

Operators

Allocation

VectorNew *VectorNew (int w, int h)

Create a new physical VectorImage with w x h vectors and return a pointer to that VectorImage.

void VectorFree (VectorImage *vectorImage)

Deallocate vectorImage.

VectorImage *VectorClip (VectorImage *vectorImage, int x, int y, int w, int h)

Create a virtual VectorImage of size w by h, with vectorImage as the parent, and offset (x, y) from the upper-left corner of vectorImage. A pointer to the new VectorImage is returned.

void VectorReclip (VectorImage *vectorImage, int x, int y, int w, int h, VectorImage *clipped)

This function is identical to VectorClip, except that it destructively modifies the virtual VectorImage clipped (instead of creating a new virtual VectorImage). Warning : memory leaks will occurs if clipped is a physical VectorImage.

Initialization

void VectorCopy (VectorImage *src, VectorImage *dest)

Copy the top-left w x h area of VectorImage src into VectorImage dest, where w and h are minimum width and height of src and dest.

Queries

int VectorGetX(VectorImage *vectorImage) int VectorGetY(VectorImage *vectorImage) int VectorGetWidth(VectorImage *vectorImage) int VectorGetHeight(VectorImage *vectorImage) int VectorGetVirtual(VectorImage *vectorImage)

These functions (macros in the C version) access various fields in the VectorImage data structure. The first two function return the x or y offset of vectorImage within its parent, the next two return the width or height of vectorImage, and the last function returns 1 if vectorImage is virtual, 0 otherwise.