[Pixman] [PATCH 03/13] pixman-image: Added GNUPLOT_OUTPUT compile-time option to view filters in gnuplot

[Oded Gabbay]

On Mon, Jan 4, 2016 at 7:34 PM, Bill Spitzak <spitzak at gmail.com> wrote:
>
>
> On Mon, Jan 4, 2016 at 3:25 AM, Oded Gabbay <oded.gabbay at gmail.com> wrote:
>>
>> On Mon, Jan 4, 2016 at 5:12 AM,  <spitzak at gmail.com> wrote:
>> > From: Bill Spitzak <spitzak at gmail.com>
>> >
>> > If GNUPLOT_OUTPUT is set, then you can pipe the output of a pixman-using
>> > program
>> > to gnuplot and get a continuously-updated plot of the horizontal filter.
>> > This
>> > works well with demos/scale to test the filter generation.
>> >
>> > The plot is all the different subposition filters shuffled together.
>> > This is
>> > misleading in a few cases:
>> >
>> >   IMPULSE.BOX - goes up and down as the subfilters have different
>> > numbers of non-zero samples
>> >   IMPULSE.TRIANGLE - somewhat crooked for the same reason
>> >   1-wide filters - looks triangular, but a 1-wide box would be more
>> > accurate
>> > ---
>> >  pixman/pixman-image.c | 40 ++++++++++++++++++++++++++++++++++++++++
>> >  1 file changed, 40 insertions(+)
>> >
>> > diff --git a/pixman/pixman-image.c b/pixman/pixman-image.c
>> > index 1ff1a49..69743c4 100644
>> > --- a/pixman/pixman-image.c
>> > +++ b/pixman/pixman-image.c
>> > @@ -531,6 +531,46 @@ compute_image_info (pixman_image_t *image)
>> >
>> >      image->common.flags = flags;
>> >      image->common.extended_format_code = code;
>> > +/* If GNUPLOT_OUTPUT is set, then you can pipe the output of a
>> > pixman-using program
>> > + * to gnuplot and get a continuously-updated plot of the horizontal
>> > filter. This
>> > + * works well with demos/scale to test the filter generation.
>> > + *
>> > + * The plot is all the different subposition filters shuffled together.
>> > This is
>> > + * misleading in a few cases:
>> > + *
>> > + *  IMPULSE.BOX - goes up and down as the subfilters have different
>> > numbers of non-zero samples
>> > + *  IMPULSE.TRIANGLE - somewhat crooked for the same reason
>> > + *  1-wide filters - looks triangular, but a 1-wide box would be more
>> > accurate
>> > + */
>> > +/* #define GNUPLOT_OUTPUT 1 */
>> > +#if GNUPLOT_OUTPUT
>> > +    if ((flags & FAST_PATH_SEPARABLE_CONVOLUTION_FILTER) &&
>> > image->common.filter_params) {
>> > +       const pixman_fixed_t* p = image->common.filter_params;
>> > +       int width = pixman_fixed_to_int(p[0]);
>> > +       int samples = 1 << pixman_fixed_to_int(p[2]);
>> > +       int x,y;
>> > +       p += 4;
>> > +       printf("plot '-' with linespoints\n");
>> > +       printf("%g 0\n", - width * .5);
>> > +       for (x = 0; x < width; ++x) {
>> > +           for (y = 0; y < samples; ++y) {
>> > +               int yy;
>> > +               if (width & 1)
>> > +                   yy = y;
>> > +               else if (y >= samples / 2)
>> > +                   yy = y - samples / 2;
>> > +               else
>> > +                   yy = samples / 2 + y;
>> > +               printf("%g %g\n",
>> > +                      x - width * .5 + (y + .5) * (1.0 / samples),
>> > +                      pixman_fixed_to_double(p[(yy + 1) * width - x -
>> > 1]));
>> > +           }
>> > +       }
>> > +       printf("%g 0\n", width * .5);
>> > +       printf("e\n");
>> > +       fflush(stdout);
>> > +    }
>> > +#endif
>> >  }
>> >
>> >  void
>> > --
>> > 1.9.1
>> >
>> > _______________________________________________
>> > Pixman mailing list
>> > Pixman at lists.freedesktop.org
>> > http://lists.freedesktop.org/mailman/listinfo/pixman
>>
>> I get the big picture of this feature, and it seems useful, but we
>> need write this according to standards.
>> I would like to see the following changes:
>>
>> 1. We can do something more nice than a hard-coded #define. Let's add
>> a flag to configure.ac called "enable-gnuplot-output". For something
>> similar, see "enable-timers" in configure.ac. The default will be
>> "no".
>
>
> That makes sense. I actually gave up trying to figure out how to set the
> CFLAGS and was forced to edit the source code to turn this on/off, which
> meant I often mistakenly checked the code in with it turned on. I guess
> configure is the way to go.
>
>>
>> 2. Take your code and put it in a new function in pixman-utils.c, and
>> make sure the code inside the function is encompassed with
>> #ifdef/#endif around it. In case enable-gluplot-output wasn't called,
>> the function will be an empty function.
>>
>> 3. Call that function from compute_image_info. I guess you will want
>> to call it only if:
>> ((flags & FAST_PATH_SEPARABLE_CONVOLUTION_FILTER) &&
>> image->common.filter_params)
>> is true.
>> However, we don't need to put #ifdef around the call itself.
>
>
> I would prefer that there not be a call to the empty function there, and
> that instead the config option removes the call to it here. In addition the
> arguments may be non-trivial as I would like this to be able to print
> filters from a future mulit-resolution data structure, to extract this from
> the current structure I need to pass the width, subsamples, and pointer to
> array.

No problem, it was just a suggestion. Do what you see fit and we'll
discuss it when you send it.

      Oded
>
>>
>> I think the above steps will create two patches:
>> - Step 1&2 should be the first patch (Adding the utility).
>> - Step 3 should be the second patch (Using the utility).
>
>
> Ok.
>
>>
>> Is using this is simple as:
>> ./<demo/test binary> | gnuplot     ?
>
>
> Yes that is how it works. It works surprisingly well. It is sometimes useful
> to go to the gnuplot window and scroll up/down a bit to lock the current
> zoom. Hit the button with the squiggle on the top to go back to auto-zoom.
>
>> If so, put an example of how to use it in the second commit message.
>>
>> Thanks,
>>
>> Oded
>
>