How to tell Canvas.pngStream() that the stream has ended?

[giacecco]

Sorry if this is a stupid question, but I can't find a solution. If I write code like the one you see below:

    var canvas = new Canvas(CARD_SIZE_X, CARD_SIZE_Y),
        out = fs.createWriteStream(__dirname + '/text' + page + '.png'),
        stream = canvas.pngStream(),
        ctx = canvas.getContext('2d');
    stream.on('data', function(chunk) { out.write(chunk); });
    stream.on('end', function() { console.log('saved png'); });

... the 'end' event of the stream is triggered when the nodejs script exits.

What method of stream or perhaps canvas should I call if I need the stream to end before that, e.g. if I want to use the file that I have just created within the same script?

Moreover, if I create many streams from different canvas, when execution ends only the last of the .png files I have created has content, while all other files have zero length.

Thanks,

Giacecco

[giacecco]

I setup a gist https://gist.github.com/giacecco/7234364 that simplifies my problem and makes evident what I am not understanding. Please help!

[mitar]

The PNG stream is underdefined. Maybe try to wrap it in a similar manner: #232 (comment)

[LinusU]

Closing this since it's an old thread, please report back if you still have problems...

[Etsitpab]

I still have the same problem with jpeg streams. The end event is only triggered when the script ends. This makes it consumming a lot of memory.

[LinusU]

@Etsitpab That does sound like a bug, but I don't think it's the same since JPEG- and PNG-streams are handled very differently. Could you open up a new bug describing your issue?

[Etsitpab]

@LinusU sorry for the delay, here is the shortest script I could write to reproduce the problem I observed :

#!/usr/bin/env node

var fs = require('fs'),
    Canvas = require('canvas'),
    Image = Canvas.Image;

(function () {
    "use strict";
    var out, stream;
    out = fs.createWriteStream("test1.jpg");
    stream = new Canvas(500, 500).syncJPEGStream();
    stream.on('data', function (chunk) {
        console.log("Write chunk for", "test1.jpg")
        out.write(chunk);
    });
    stream.on('end', function () {
        console.log("End stream for", "test1.jpg")
    });
    out = fs.createWriteStream("test2.jpg");
    stream = new Canvas(500, 500).syncJPEGStream();
    stream.on('data', function (chunk) {
        console.log("Write chunk for", "test2.jpg")
        out.write(chunk);
    });
    stream.on('end', function () {
        console.log("End stream for", "test2.jpg")
    });
})();

And here, the corresponding output:

Write chunk for test1.jpg
Write chunk for test2.jpg
Write chunk for test2.jpg
End stream for test2.jpg
Write chunk for test1.jpg
End stream for test1.jpg

Where I was expecting something like that:

Write chunk for test1.jpg
Write chunk for test1.jpg
End stream for test1.jpg
Write chunk for test2.jpg
Write chunk for test2.jpg
End stream for test2.jpg

I'm very interested to know whether you are able to reproduce this behavioror have any hint on what i could do wrong. Thank you for your time and for the great work you're doing, this module is really cool !

[mitar]

@Etsitpab, please open a new ticket and put all this information there.

[LinusU]

Output for me:

Write chunk for test1.jpg
Write chunk for test1.jpg
End stream for test1.jpg
Write chunk for test2.jpg
Write chunk for test2.jpg
End stream for test2.jpg

[Etsitpab]

Well, I don't know why it doesn't work. Looks like we are stuck.
I'm using Debian sid by the way but I have another laptop under Ubuntu. I
will try as soon as possible if I also have this problem with it.

Thank you very much.
Baptiste

2016-03-07 13:19 GMT+01:00 Linus Unnebäck [email protected]:

Output for me:

Write chunk for test1.jpg
Write chunk for test1.jpg
End stream for test1.jpg
Write chunk for test2.jpg
Write chunk for test2.jpg
End stream for test2.jpg

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#351 (comment)
.

[LinusU]

I'm using OS X without pango installed...

[Etsitpab]

Ok, do you think that I could be related or that I should try something
like uninstalling pango ?

2016-03-07 13:33 GMT+01:00 Linus Unnebäck [email protected]:

I'm using OS X without pango installed...

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#351 (comment)
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[LinusU]

Hmm, I don't think that it's related, but you never know :)

[Etsitpab]

I tried to uninstall it, but I doesn't make any difference :-(

2016-03-07 13:35 GMT+01:00 Linus Unnebäck [email protected]:

Hmm, I don't think that it's related, but you never know :)

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#351 (comment)
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[LinusU]

Did you run node-gyp rebuild afterwards?

[Etsitpab]

No, I have to get back to work, I will try it tonight. thank you very much
for your help !
Cheers,
Baptiste

2016-03-07 13:41 GMT+01:00 Linus Unnebäck [email protected]:

Did you run node-gyp rebuild afterwards?

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[LinusU]

No problem 👍