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have written new "effect" for geometrictransform

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Bert Douglas

have written new "effect" for geometrictransform

Hi All,

I have written a new "effect" for geometrictransform. It does image rotation.
The code is appended below.
If there is any interest, I will do the work to push it upstream.
But I need a mentor to help guide the way.

On the code itself.
I modified the "circle" element, to do rotation.
The changes were confined to the "map" function.
I used the same parameters, but with different meaning.

Thanks,
Bert Douglas

------------------------------------------------------------------------

static gboolean
circle_map (GstGeometricTransform * gt, gint x, gint y, gdouble * in_x,
    gdouble * in_y)
{
//GstCircleGeometricTransform *cgt = GST_CIRCLE_GEOMETRIC_TRANSFORM_CAST (gt);
GstCircle *circle = GST_CIRCLE_CAST (gt);

gint w, h;
gdouble pad, sa;
gdouble cix, ciy, cox, coy;   // centers, in/out x/y
gdouble ai, ao, ar;           // angles, in/out/rotate (radians)
gdouble r;                    // radius
gdouble xi, yi, xo, yo;       // positions in/out x/y

// input and output image height and width
w = gt->width;
h = gt->height;

// our parameters
pad = circle->height;         // padding on bottom and right of input image
ar = circle->angle * M_PI / 180.0;    // angle of rotation, degrees to radians
sa = circle->spread_angle;    // not used

// get in and out centers
cox = 0.5 * w;
coy = 0.5 * h;
cix = 0.5 * (w - pad);
ciy = 0.5 * (h - pad);

// convert output image position to polar form
xo = x - cox;
yo = y - coy;
ao = atan2 (yo, xo);
r = sqrt (xo * xo + yo * yo);

// perform rotation backward to get input image rotation
// this seems wrong, but rotation from in-->out is counterclockwise
ai = ao + ar;

// back to rectangular for input image position
xi = r * cos (ai);
yi = r * sin (ai);

// restore center offset, return values to caller
*in_x = xi + cix;
*in_y = yi + ciy;

GST_DEBUG_OBJECT (circle, "Inversely mapped %d %d into %lf %lf",
      x, y, *in_x, *in_y);

return TRUE;
}

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Thiago Sousa Santos-2

Re: have written new "effect" for geometrictransform

On Thu, Sep 2, 2010 at 9:45 AM, Bert Douglas <[hidden email]> wrote:

Hi All,

I have written a new "effect" for geometrictransform. It does image rotation.
The code is appended below.
If there is any interest, I will do the work to push it upstream.
But I need a mentor to help guide the way.

On the code itself.
I modified the "circle" element, to do rotation.
The changes were confined to the "map" function.
I used the same parameters, but with different meaning.

Great! I can help you getting this in. Can you provide this as a git patch in bugzilla?

In case you've never done this before, I could guide you through the details so you'd learn how to do it. I'm available on #gstreamer on freenode as 'thiagoss'. You can talk to me there or send me a private mail.

Thanks,
Bert Douglas

------------------------------------------------------------------------

static gboolean
circle_map (GstGeometricTransform * gt, gint x, gint y, gdouble * in_x,
    gdouble * in_y)
{
//GstCircleGeometricTransform *cgt = GST_CIRCLE_GEOMETRIC_TRANSFORM_CAST (gt);
GstCircle *circle = GST_CIRCLE_CAST (gt);

gint w, h;
gdouble pad, sa;
gdouble cix, ciy, cox, coy;   // centers, in/out x/y
gdouble ai, ao, ar;           // angles, in/out/rotate (radians)
gdouble r;                    // radius
gdouble xi, yi, xo, yo;       // positions in/out x/y

// input and output image height and width
w = gt->width;
h = gt->height;

// our parameters
pad = circle->height;         // padding on bottom and right of input image
ar = circle->angle * M_PI / 180.0;    // angle of rotation, degrees to radians
sa = circle->spread_angle;    // not used

// get in and out centers
cox = 0.5 * w;
coy = 0.5 * h;
cix = 0.5 * (w - pad);
ciy = 0.5 * (h - pad);

// convert output image position to polar form
xo = x - cox;
yo = y - coy;
ao = atan2 (yo, xo);
r = sqrt (xo * xo + yo * yo);

// perform rotation backward to get input image rotation
// this seems wrong, but rotation from in-->out is counterclockwise
ai = ao + ar;

// back to rectangular for input image position
xi = r * cos (ai);
yi = r * sin (ai);

// restore center offset, return values to caller
*in_x = xi + cix;
*in_y = yi + ciy;

GST_DEBUG_OBJECT (circle, "Inversely mapped %d %d into %lf %lf",
      x, y, *in_x, *in_y);

return TRUE;
}

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--
Thiago Sousa Santos

------------------------------------------------------------------------------
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Show off your parallel programming skills.
Enter the Intel(R) Threading Challenge 2010.
http://p.sf.net/sfu/intel-thread-sfd
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