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• Perspective transformations

  9 juin 2010, par Mikko Koppanen — Imagick, PHP stuff

  Finally (after a long break) I managed to force myself to update the PHP documentation and this time it was distortImage code example. Things have been hectic lately but that does not quite explain the 6 months(?) break between this and the previous post. As a matter of a fact there is no excuse for such a long silence so I will try to update this blog a bit more often from now on.

  Back in the day I used to blog the examples and update the documentation if I remembered but I am trying to fix this bad habit. Most of the latest examples have been updated in to the manual. In the case of the two last examples I updated the documentation first and then blogged on the subject.

  I took some time to actually understand the perspective transformations properly using the excellent ImageMagick examples (mainly created by Anthony Thyssen) as a reference. The basic idea of perspective distortion seems simple : to distort the control points to new locations. Grabbing the syntax for Imagick was easy, an array of control point pairs in the form of :

  php

  < view plain text >

  1. array(source_x, source_y, dest_x, dest_y ... )

  The following example uses the built-in checkerboard pattern to demonstrate perspective distortion :

  php

  < view plain text >

  1. < ?php
  2. /* Create new object */
  3. $im = new Imagick() ;
  4.  
  5. /* Create new checkerboard pattern */
  6. $im->newPseudoImage(100, 100, "pattern:checkerboard") ;
  7.  
  8. /* Set the image format to png */
  9. $im->setImageFormat(’png’) ;
  10.  
  11. /* Fill background area with transparent */
  12. $im->setImageVirtualPixelMethod(Imagick: :VIRTUALPIXELMETHOD_TRANSPARENT) ;
  13.  
  14. /* Activate matte */
  15. $im->setImageMatte(true) ;
  16.  
  17. /* Control points for the distortion */
  18. $controlPoints = array( 10, 10,
  19.             10, 5,
  20.  
  21.             10, $im->getImageHeight() - 20,
  22.             10, $im->getImageHeight() - 5,
  23.  
  24.             $im->getImageWidth() - 10, 10,
  25.             $im->getImageWidth() - 10, 20,
  26.  
  27.             $im->getImageWidth() - 10, $im->getImageHeight() - 10,
  28.             $im->getImageWidth() - 10, $im->getImageHeight() - 30) ;
  29.  
  30. /* Perform the distortion */ 
  31. $im->distortImage(Imagick: :DISTORTION_PERSPECTIVE, $controlPoints, true) ;
  32.  
  33. /* Ouput the image */ 
  34. header("Content-Type : image/png") ;
  35. echo $im ;
  36.  ?>

  Here is the source image :
  

  And the result :
  

• Revision 33982 : oups, layout.html devient structure.html

  27 décembre 2009, par cedric@… — Log

  oups, layout.html devient structure.html

• FFmpeg matlab error : At least one output file must be specified ? [closed]

  3 mars, par as moh

  I'm trying to get I frames from a video using Matlab using this command system(sprintf('ffmpeg -i testVid.mp4 -vf "select=eq(pict_type\,I)" -vsync vfr output_%03d.png')); ,but i get this message

  &#xA;

   ffmpeg version 7.1-full_build-www.gyan.dev Copyright (c) 2000-2024 the FFmpeg developers 
  built with gcc 14.2.0 (Rev1, Built by MSYS2 project) 
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libaribcaption --enable-libdav1d --enable-libdavs2 --enable-libopenjpeg --enable-libquirc --enable-libuavs3d --enable-libxevd --enable-libzvbi --enable-libqrencode --enable-librav1e --enable-libsvtav1 --enable-libvvenc --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxeve --enable-libxvid --enable-libaom --enable-libjxl --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libharfbuzz --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-dxva2 --enable-d3d11va --enable-d3d12va --enable-ffnvcodec --enable-libvpl --enable-nvdec --enable-nvenc --enable-vaapi --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libcodec2 --enable-libilbc --enable-libgsm --enable-liblc3 --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint 
  libavutil      59. 39.100 / 59. 39.100 
  libavcodec     61. 19.100 / 61. 19.100 
  libavformat    61.  7.100 / 61.  7.100 
  libavdevice    61.  3.100 / 61.  3.100 
  libavfilter    10.  4.100 / 10.  4.100 
  libswscale      8.  3.100 /  8.  3.100 
  libswresample   5.  3.100 /  5.  3.100 
  libpostproc    58.  3.100 / 58.  3.100 
Trailing option(s) found in the command: may be ignored. 
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'testVid.mp4': 
  Metadata: 
    major_brand     : isom 
    minor_version   : 512 
    compatible_brands: isomiso2avc1mp41 
    encoder         : Lavf57.83.100 
  Duration: 00:00:02.02, start: 0.000000, bitrate: 12798 kb/s 
  Stream #0:0[0x1](eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuvj420p(pc, progressive), 1280x720 [SAR 1:1 DAR 16:9], 12662 kb/s, 29.74 fps, 30 tbr, 90k tbn (default) 
      Metadata: 
        handler_name    : VideoHandler 
        vendor_id       : [0][0][0][0] 
  Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 121 kb/s (default) 
      Metadata: 
        handler_name    : SoundHandler 
        vendor_id       : [0][0][0][0] 
At least one output file must be specified 


  &#xA;

  i searched and tried many cases but i don't know where is the problem, any help please ?

  &#xA;