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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 :
  

• Node js async/await promise problem with ytdl and ffmpeg

  31 août 2020, par WorkoutBuddy

  I built a simple youtube downloader cli. It looks like this (without any arg parsing for easier reproduction) :

  &#xA;

  const ytdl = require('ytdl-core');
const config = require('config');
const progressBar = require('./progressBar');
const logger = require('./logger');
const ffmpeg = require('fluent-ffmpeg');

const url = 'https://www.youtube.com/watch?v=Np8ibIagn3M';

const getInfo = async (url) => {
    logger.info(`Getting metadata for ${url}`);
    const response = await ytdl.getBasicInfo(url);
    const info = response.videoDetails.title;
    logger.info(`Title: ${info}`);
    return info;
};

const getStream = async (url) => {
    logger.info(`Downloading from ${url} ...`);

    let allReceived = false;
    return new Promise((resolve, reject) => {
        const stream = ytdl(url, {
            quality: 'highest',
            filter: (format) => format.container === 'mp4',
        })
            .on('progress', (_, totalDownloaded, total) => {
                if (!allReceived) {
                    progressBar.start(total, 0, {
                        mbTotal: (total / 1024 / 1024).toFixed(2),
                        mbValue: 0,
                    });
                    allReceived = true;
                }
                progressBar.increment();
                progressBar.update(totalDownloaded, {
                    mbValue: (totalDownloaded / 1024 / 1024).toFixed(2),
                });
            })
            .on('end', () => {
                progressBar.stop();
                logger.info('Successfully downloaded the stream!');
            });
        return resolve(stream);
    });
};

const convertToMp3 = async (stream, title) => {
    return new Promise((resolve, reject) => {
        ffmpeg({ source: stream })
            .output(`${config.get('audioDir')}/${title}.mp3`)
            .audioBitrate('192k')
            .run();
        return resolve();
    });
};

const main = async (url) => {
    const info = await getInfo(url);
    console.log('here 1');
    const stream = await getStream(url);
    console.log('here 2');
    await convertToMp3(stream, info);
    console.log('done');
};

main(url);


  &#xA;

  The output looks like :

  &#xA;

  ➜ node youtube.js
info:    Getting metadata for https://www.youtube.com/watch?v=Np8ibIagn3M
info:    Title: Tu boca -  (Bachata Remix Dj Khalid)
here 1
info:    Downloading from https://www.youtube.com/watch?v=Np8ibIagn3M ...
here 2
done
[Progress] [████████████████████████████████████████] 100% | Downloaded: 7.15/7.15 MB | Elapsed Time: 5s
info:    Successfully downloaded the stream!


  &#xA;

  However, I would expect this output :

  &#xA;

  ➜ node youtube.js
info:    Getting metadata for https://www.youtube.com/watch?v=Np8ibIagn3M
info:    Title: Tu boca -  (Bachata Remix Dj Khalid)
here 1
info:    Downloading from https://www.youtube.com/watch?v=Np8ibIagn3M ...
[Progress] [████████████████████████████████████████] 100% | Downloaded: 7.15/7.15 MB | Elapsed Time: 5s
here 2
info:    Successfully downloaded the stream!
done


  &#xA;

  I think I have troubles to understand async/await. As far as I understood, promisifying a function allows me wait for the result. However, it seems that it does not work. I do not know why and how to properly debug it.

  &#xA;

  EDITED :

  &#xA;

  const getStream = async (url) => {
    logger.info(`Downloading from ${url} ...`);

    let allReceived = false;
    return new Promise((resolve, reject) => {
        const stream = ytdl(url, {
            quality: 'highest',
            filter: (format) => format.container === 'mp4',
        })
            .on('progress', (_, totalDownloaded, total) => {
                console.log('totalDownloaded: ' + totalDownloaded);
                if (!allReceived) {
                    console.log('total: ' + total);
                    progressBar.start(total, 0, {
                        mbTotal: (total / 1024 / 1024).toFixed(2),
                        mbValue: 0,
                    });
                    allReceived = true;
                }
                progressBar.increment();
                progressBar.update(totalDownloaded, {
                    mbValue: (totalDownloaded / 1024 / 1024).toFixed(2),
                });
            })
            .on('end', () => {
                progressBar.stop();
                logger.info('Successfully downloaded the stream!');
                resolve(stream);
            });
    });
};


  &#xA;

  But now it is like this :

  &#xA;

  ➜ node youtube.js
info:    Getting metadata for https://www.youtube.com/watch?v=Np8ibIagn3M
info:    Title: Tu boca -  (Bachata Remix Dj Khalid)
here 1
info:    Downloading from https://www.youtube.com/watch?v=Np8ibIagn3M ...
[Progress] [██████░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░] 14% | Downloaded: 1.02/7.15 MB | Elapsed Time: 52s


  &#xA;

  Added console.log :

  &#xA;

  totalDownloaded: 16384
total: 7493903
[Progress] [░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░] 0% | Downloaded: 0/7.15 MB | Elapsed Time: 0stotalDownloaded: 32768
totalDownloaded: 49152
totalDownloaded: 65536
totalDownloaded: 81920
totalDownloaded: 98304
totalDownloaded: 114688
totalDownloaded: 131072
totalDownloaded: 147456
totalDownloaded: 163840
totalDownloaded: 180224
totalDownloaded: 196608
totalDownloaded: 212992
totalDownloaded: 229376
totalDownloaded: 245760
totalDownloaded: 262144
totalDownloaded: 278528
totalDownloaded: 294912
totalDownloaded: 311296
totalDownloaded: 327680
totalDownloaded: 344064
totalDownloaded: 360448
totalDownloaded: 376832
totalDownloaded: 393216
totalDownloaded: 409600
totalDownloaded: 425984
totalDownloaded: 442368
totalDownloaded: 458752
totalDownloaded: 475136
totalDownloaded: 491520
totalDownloaded: 507904
totalDownloaded: 524288
totalDownloaded: 540672
totalDownloaded: 557056
totalDownloaded: 573440
totalDownloaded: 589824
totalDownloaded: 606208
totalDownloaded: 622592
totalDownloaded: 638976
totalDownloaded: 655360
totalDownloaded: 671744
totalDownloaded: 688128
totalDownloaded: 704512
totalDownloaded: 720896
totalDownloaded: 737280
totalDownloaded: 753664
totalDownloaded: 770048
totalDownloaded: 786432
totalDownloaded: 802816
totalDownloaded: 819200
totalDownloaded: 835584
totalDownloaded: 851968
totalDownloaded: 868352
totalDownloaded: 884736
totalDownloaded: 901120
totalDownloaded: 917504
totalDownloaded: 933888
totalDownloaded: 950272
totalDownloaded: 966656
totalDownloaded: 983040
totalDownloaded: 999424
totalDownloaded: 1015808
totalDownloaded: 1032192
totalDownloaded: 1048576
totalDownloaded: 1064960
[Progress] [██████░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░] 14% | Downloaded: 1.02/7.15 MB | Elapsed Time: 25s


  &#xA;