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• About image opacity

  23 octobre 2013, par Mikko Koppanen — Imagick

  There is a common misconception that Imagick::setImageOpacity() would work to reduce the opacity of the image. However, as the name says the method actually sets the opacity throughout the image and thus affects also transparent areas.

  To demonstrate let’s first look at this image of a red circle on a transparent background :

  

  Now, let’s apply setImageOpacity on the image :

  php

  < view plain text >

  1. < ?php
  2. $im = new Imagick (’red-circle.png’) ;
  3. $im->setImageOpacity (0.5) ;
  4. $im->writeImage (’red-circle-setopacity.png’) ;
  5.  ?>

  

  As we can see from the resulting image the transparent background is affected as well.

  In order to actually reduce the opacity of the opaque parts Imagick::evaluateImage can be used instead :

  php

  < view plain text >

  1. < ?php
  2. $im = new Imagick (’red-circle.png’) ;
  3.  
  4. /* Divide the alpha channel value by 2 */
  5. $im->evaluateImage(Imagick: :EVALUATE_DIVIDE, 2, Imagick: :CHANNEL_ALPHA) ;
  6. $im->writeImage (’red-circle-divide.png’) ;
  7.  ?>

  And here are the results :

  

  As the background is already fully transparent so the divide operation causes no changes to it.

  Similar example is available in the PHP manual http://php.net/imagick.evaluateimage and I added a note to setImageOpacity page as well (at the time of writing it has not synced to documentation mirrors yet).

• d3d11va : Check WINAPI_FAMILY instead of HAVE_LOADLIBRARY

  4 juillet 2017, par Martin Storsjö

  d3d11va : Check WINAPI_FAMILY instead of HAVE_LOADLIBRARY
  If using the winstore compat library, a fallback LoadLibrary
  
  function does exist, that only calls LoadPackagedLibrary though
  
  (which doesn’t work for dynamically loading d3d11 DLLs).
  Therefore explicitly check the targeted API family instead.
  Make this check a reusable HAVE_* component which other parts
  
  of the libraries can check when necessary as well.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] configure
  • [DBH] libavutil/hwcontext_d3d11va.c

• Ffmpeg is installed, but I get the exception : You do not have ffmpeg installed on your machine

  13 janvier 2023, par Tin Kommen

  I've searched for hours for a solution, but I haven't found one yet. Maybe someone here knows what is going wrong.

  &#xA;

  I'm trying to make a Bar Chart Race in Python. Although I have downloaded and installed Ffmpeg,&#xA;I keep on getting multiple errors :

  &#xA;

      MovieWriter ffmpeg unavailable; using Pillow instead.
    Traceback (most recent call last):
      File "/Users/___/PycharmProjects/data_visualization/venv/lib/python3.6/site-        packages/matplotlib/animation.py", line 251, in saving
        yield self
      File "/Users/___/PycharmProjects/data_visualization/venv/lib/python3.6/site-        packages/matplotlib/animation.py", line 1161, in save
        writer.grab_frame(**savefig_kwargs)
      File "/Users/____/PycharmProjects/data_visualization/venv/lib/python3.6/site-        packages/matplotlib/animation.py", line 549, in grab_frame
        renderer = self.fig.canvas.get_renderer()
    AttributeError: 'FigureCanvasBase' object has no attribute 'get_renderer'

    During handling of the above exception, another exception occurred:

    Traceback (most recent call last):
      File "/Users/___/PycharmProjects/data_visualization/venv/lib/python3.6/site-        packages/bar_chart_race/_make_chart.py", line 435, in make_animation
        ret_val = anim.save(self.filename, fps=self.fps, writer=self.writer)
      File "/Users/___/PycharmProjects/data_visualization/venv/lib/python3.6/site-        packages/matplotlib/animation.py", line 1161, in save
        writer.grab_frame(**savefig_kwargs)
      File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/contextlib.py", line         100, in __exit__
        self.gen.throw(type, value, traceback)
      File "/Users/___/PycharmProjects/data_visualization/venv/lib/python3.6/site-                        packages/matplotlib/animation.py", line 253, in saving
        self.finish()
              File "/Users/____/PycharmProjects/data_visualization/venv/lib/python3.6/site-        packages/matplotlib/animation.py", line 554, in finish
        self._frames[0].save(
            IndexError: list index out of range

    During handling of the above exception, another exception occurred:

    Exception: You do not have ffmpeg installed on your machine. Download
    ffmpeg from here: https://www.ffmpeg.org/download.html.
    Matplotlib's original error message below:
    list index out of range


  &#xA;

  I've tried installing ffmpeg with conda, pip and homebrew. When I check the version, i get the following :

  &#xA;

      ffmpeg version 4.2.3 Copyright (c) 2000-2020 the FFmpeg developers
      built with clang version 9.0.1
      configuration: --prefix=/Users/___/opt/miniconda3 --cc=x86_64-apple-darwin13.4.0-clang --disable-doc --disable-openssl --enable-avresample --enable-gnutls --enable-gpl --enable-hardcoded-tables --enable-libfreetype --enable-libopenh264 --enable-libx264 --enable-pic --enable-pthreads --enable-shared --enable-static --enable-version3 --enable-zlib --enable-libmp3lame
      libavutil      56. 31.100 / 56. 31.100
      libavcodec     58. 54.100 / 58. 54.100
      libavformat    58. 29.100 / 58. 29.100
      libavdevice    58.  8.100 / 58.  8.100
      libavfilter     7. 57.100 /  7. 57.100
      libavresample   4.  0.  0 /  4.  0.  0
      libswscale      5.  5.100 /  5.  5.100
      libswresample   3.  5.100 /  3.  5.100
      libpostproc    55.  5.100 / 55.  5.100


  &#xA;

  Here is the code :

  &#xA;

      import numpy as np
    import pandas as pd
    import bar_chart_race as bcr
    import os



    df = pd.read_csv('/Users/____/Documents/data/dummy_data.csv', delimiter=';', encoding="utf-8-sig")
    bcr.bar_chart_race(
        df=df,
        filename='test_win2.mov',
        orientation='h',
        sort='desc',
        n_bars=8,
        fixed_order=False,
        fixed_max=False,
        steps_per_period=50,
        interpolate_period=False,
        label_bars=True,
        bar_size=.95,
        period_label={'x': .99, 'y': .25, 'ha': 'right', 'va': 'center'},
        period_summary_func=lambda v, r: {'x': .99, 'y': .18,
                                  's': f'Totaal: {v.nlargest(8).sum():,.0f}',
                                  'ha': 'right', 'size': 8, 'family': 'Courier New'},
        perpendicular_bar_func='median',
        figsize=(3.5, 3),
        period_length=100,
        dpi=300,
        cmap='dark12',
        title='Title?',
        title_size='',
        bar_label_size=4,
        tick_label_size=4,
        shared_fontdict={'family': 'Helvetica', 'color': '.1'},
        scale='linear',
        writer=None,
        fig=None,
        bar_kwargs={'alpha': .3},
        filter_column_colors=False)


  &#xA;