matrix downsampling C

I have a 1280x720 buffered matrix and i would like to implement a downsampling method which take one sample each 9 in both directions.

For example:

122222221222222212222222122222221222222221222222221.......

111111.....

so i implement this method:

int16_t* resample(int16_t *in_b){

    int scale=9,W=1280,H=720;

    int w=W/scale;

    int h=H/scale;

    int16_t *out_b=(int16_t*)malloc(w*h*sizeof(int16_t));

    for (i=0;i<h;i++){

        for (j=0;j<w;j++){

            out_b[i*w+j]=in_b[(i*W*scale)+(j*scale)];

        }

    }

    return out_b;

}

but if i draw an heatmap of the output it shows that input is repeated twice, what i'm wrong?

asked Nov 22 at 21:30

sdrabb

72211

1

I don’t think you’re doing anything wrong.
– Cris Luengo
Nov 23 at 2:12

...not in the code you exposed. (At least, I cannot see something wrong.) May be, the error happens anywhere else or it's the correct result you just didn't expect.
– Scheff
Nov 23 at 6:52

add a comment |

I have a 1280x720 buffered matrix and i would like to implement a downsampling method which take one sample each 9 in both directions.

For example:

122222221222222212222222122222221222222221222222221.......

111111.....

so i implement this method:

int16_t* resample(int16_t *in_b){

    int scale=9,W=1280,H=720;

    int w=W/scale;

    int h=H/scale;

    int16_t *out_b=(int16_t*)malloc(w*h*sizeof(int16_t));

    for (i=0;i<h;i++){

        for (j=0;j<w;j++){

            out_b[i*w+j]=in_b[(i*W*scale)+(j*scale)];

        }

    }

    return out_b;

}

but if i draw an heatmap of the output it shows that input is repeated twice, what i'm wrong?

asked Nov 22 at 21:30

sdrabb

72211

1

I don’t think you’re doing anything wrong.
– Cris Luengo
Nov 23 at 2:12

...not in the code you exposed. (At least, I cannot see something wrong.) May be, the error happens anywhere else or it's the correct result you just didn't expect.
– Scheff
Nov 23 at 6:52

add a comment |

I have a 1280x720 buffered matrix and i would like to implement a downsampling method which take one sample each 9 in both directions.

For example:

122222221222222212222222122222221222222221222222221.......

111111.....

so i implement this method:

int16_t* resample(int16_t *in_b){

    int scale=9,W=1280,H=720;

    int w=W/scale;

    int h=H/scale;

    int16_t *out_b=(int16_t*)malloc(w*h*sizeof(int16_t));

    for (i=0;i<h;i++){

        for (j=0;j<w;j++){

            out_b[i*w+j]=in_b[(i*W*scale)+(j*scale)];

        }

    }

    return out_b;

}

but if i draw an heatmap of the output it shows that input is repeated twice, what i'm wrong?

asked Nov 22 at 21:30

sdrabb

72211

I have a 1280x720 buffered matrix and i would like to implement a downsampling method which take one sample each 9 in both directions.

For example:

122222221222222212222222122222221222222221222222221.......

111111.....

so i implement this method:

int16_t* resample(int16_t *in_b){

    int scale=9,W=1280,H=720;

    int w=W/scale;

    int h=H/scale;

    int16_t *out_b=(int16_t*)malloc(w*h*sizeof(int16_t));

    for (i=0;i<h;i++){

        for (j=0;j<w;j++){

            out_b[i*w+j]=in_b[(i*W*scale)+(j*scale)];

        }

    }

    return out_b;

}

but if i draw an heatmap of the output it shows that input is repeated twice, what i'm wrong?

c image-processing resampling

asked Nov 22 at 21:30

sdrabb

72211

asked Nov 22 at 21:30

sdrabb

72211

asked Nov 22 at 21:30

sdrabb

72211

asked Nov 22 at 21:30

sdrabb

72211

asked Nov 22 at 21:30

sdrabb

72211

1

I don’t think you’re doing anything wrong.
– Cris Luengo
Nov 23 at 2:12

...not in the code you exposed. (At least, I cannot see something wrong.) May be, the error happens anywhere else or it's the correct result you just didn't expect.
– Scheff
Nov 23 at 6:52

add a comment |

1

I don’t think you’re doing anything wrong.
– Cris Luengo
Nov 23 at 2:12

...not in the code you exposed. (At least, I cannot see something wrong.) May be, the error happens anywhere else or it's the correct result you just didn't expect.
– Scheff
Nov 23 at 6:52

I don’t think you’re doing anything wrong.
– Cris Luengo
Nov 23 at 2:12

...not in the code you exposed. (At least, I cannot see something wrong.) May be, the error happens anywhere else or it's the correct result you just didn't expect.
– Scheff
Nov 23 at 6:52

add a comment |

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