Is OpenVX warpAffine accept a transposed matrix and how does it defined as row major?

Question

I am new to OpenVX, learning from the document that OpenVX uses a row-major storage. And the below matrix access example illustrate it, just like the ordinary row-major access pattern as we used in plain C code.

Then I go to the vx_matrix and vxCreateMatrix document page. The former has such statements:

VX_MATRIX_ROWS - The M dimension of the matrix [REQ-1131]. Read-only [REQ-1132]. Use a vx_size parameter.

VX_MATRIX_COLUMNS - The N dimension of the matrix [REQ-1133]. Read-only [REQ-1134]. Use a vx_size parameter.

While the latter said:

vx_matrix vxCreateMatrix(
    vx_context                                  c,
    vx_enum                                     data_type,
    vx_size                                     columns,
    vx_size                                     rows);

So according to my comprehension, in OpenVX world, when i said an MxN matrix, M refers to the row size and N refers to the column size. And the vxCreateMatrix declaration just follow what the row-major storage said, parameter column first and then row.

However, it really confuses me when i reach Warp Affine page, it said:

This kernel performs an affine transform with a 2x3 Matrix M with this method of pixel coordinate translation [REQ-0498]:

And the C declartion:

// x0 = a x + b y + c;
// y0 = d x + e y + f;
vx_float32 mat[3][2] = {
    {a, d}, // 'x' coefficients
    {b, e}, // 'y' coefficients
    {c, f}, // 'offsets'
};
vx_matrix matrix = vxCreateMatrix(context, VX_TYPE_FLOAT32, 2, 3);
vxCopyMatrix(matrix, mat, VX_WRITE_ONLY, VX_MEMORY_TYPE_HOST);

If the M is a 2x3 matrix, according to the previous section, it should has 2 row and 3 column. Then why should it be declared as mat[3][2] and createMatrix accept column=2 and row=3 as argument? Is my comprehension totally wrong?

Is OpenVX warpAffine accept a transposed matrix and how does it defined as row major?

Answers (1)

Related Questions