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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).

• Ruby on Rails : FFMPEG fails after upgrade Mountain Lion to Mavericks

  25 octobre 2013, par CristianOrellanaBak

  yesterday I upgrade my OS fom Mountain Lion to Mavericks and all goes well until recently.

  We are developing a Ruby on Rails v3.2.13 application for manage videos (only MP4), which worked fine until yesterday with Mountain Lion. Today (with Mavericks) I try to upload a video but get the following error in the console :

  Running transcoding...
  
  ffmpeg -y -i /Users/ME/Documents/workspace/rails/rails3-devise/public/uploads/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.mp4 -ss 0 -s 180x110 -vframes 1 -f image2 -aspect 1.6363636363636365 /Users/Me/Documents/workspace/rails/rails3-devise/public/uploads/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.png
  
  
  
  Transcoding of /Users/Me/Documents/workspace/rails/rails3-devise/public/uploads/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.mp4 to /Users/Me/Documents/workspace/railspublic/uploads/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.png succeeded
  
  
  
  Running transcoding...
  
  ffmpeg -y -i /Users/Me/Documents/workspace/rails/public/uploads/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.mp4 -ss 0 -s 180x110 -vframes 1 -f image2 -aspect 1.6363636363636365 /Users/Me/Documents/workspace/rails/rails3-devise/public/uploads/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.png
  
  
  
  Failed encoding...
  
  ffmpeg -y -i /Users/Me/Documents/workspace/rails/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.mp4 -ss 0 -s 180x110 -vframes 1 -f image2 -aspect 1.6363636363636365 /Users/Me/Documents/workspace/rails/uploads/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.png
  
  
  
  ffmpeg version 1.2.1 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Sep 28 2013 20:09:07 with Apple LLVM version 4.2 (clang-425.0.24) (based on LLVM 3.2svn)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/1.2.1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --enable-vda --cc=cc --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid --enable-libfreetype --enable-libtheora --enable-libvorbis --enable-libvpx --enable-librtmp --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-aacenc --enable-libass --enable-ffplay --enable-libspeex --enable-libschroedinger --enable-libfdk-aac --enable-libopus --enable-frei0r --enable-libopenjpeg --extra-cflags='-I/usr/local/Cellar/openjpeg/1.5.1/include/openjpeg-1.5 '
  
    libavutil      52. 18.100 / 52. 18.100
  
    libavcodec     54. 92.100 / 54. 92.100
  
    libavformat    54. 63.104 / 54. 63.104
  
    libavdevice    54.  3.103 / 54.  3.103
  
    libavfilter     3. 42.103 /  3. 42.103
  
    libswscale      2.  2.100 /  2.  2.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  2.100 / 52.  2.100
  
  [mp3 @ 0x7fd493820c00] Format mp3 detected only with low score of 1, misdetection possible!
  
  [mp3 @ 0x7fd49380a000] Header missing
  
      Last message repeated 1 times
  
  [mp3 @ 0x7fd493820c00] decoding for stream 0 failed
  
  [mp3 @ 0x7fd493820c00] Could not find codec parameters for stream 0 (Audio: mp2, 0 channels, s16p): unspecified frame size
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  [mp3 @ 0x7fd493820c00] Estimating duration from bitrate, this may be inaccurate
  
  /Users/Me/Documents/workspace/rails/tmp/1382653048-574-3293/thumb_con02_apv_revisado_1280x720.mp4: could not find codec parameters
  
  
  
  Errors: no output file created.

  I reinstall the dependencies of ffmpeg, but the problem persists.

  Any ideas or suggestions to solve the problem ?
  Thank you very much !

  EDIT NOTE : I notice this when run brew upgrade :

  ==> Upgrading ffmpeg
  
  ==> Installing ffmpeg dependency: libass
  
  Error: libass dependency fontconfig was built with the following
  
  C++ standard library: libstdc++ (from clang)
  
  
  
  This is incompatible with the standard library being used
  
  to build libass: libc++ (from clang)
  
  
  
  Please reinstall fontconfig using a compatible compiler.
  
  hint: Check https://github.com/mxcl/homebrew/wiki/C++-Standard-Libraries

• Live Video Streaming from android device to server [on hold]

  23 octobre 2013, par Android_sp

  hey friends i want your help

  i search a lot and study lots of code available for streaming for android but yet i can't get clear idea for me. i want simple one thing to pass stream from android device to wowza server in H.264 encoding for video and AAC for Audio.

  here some links which i already serf :

  Which not anwser :Link 1

  i also refer this most popular question from our site : Link 2

  but this useful but at some level ..

  1) Native side by using FFmpeg library i can able to send video stream but can't find a way how to encode video in H.264 format : Downloaded from here

  2) SPYdroid demo i found but from this i can send video stream to particular server :
  Downloaded from Here

  so guys if you know some thing please help me so i can find a way.