Promises Support about lwip HOT 17 CLOSED

@gkaimakas Promises support would indeed make a nice feature.
However, I'm not sure I want to incorporate it as part of the core module, as it would add much overhead.

Maybe a new lwip-promise module is in order, which will wrap the original lwip module with support for promises.
Also worth checking Bluebird's PromisifyAll.

Something like this would be nice:

lwip.open('image.jpg')
    .then(function(image){
        return image.scale(0.5);
    })
    .then(function(image){
        return image.rotate(45);
    })
    .catch(function(err){
        // ...
    });

I'm open for discussion on what's the best approach.
If anybody else would like support for promises please let me know here.

Thanks.

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I was thinking exactly the same thing as the code you posted!
On Nov 15, 2014 12:27 PM, "Eyal Arubas" [email protected] wrote:

@gkaimakas https://github.com/gkaimakas Promises support would indeed
make a nice feature.
However, I'm not sure I want to incorporate it as part of the core module,
as it would add much overhead.

Maybe a new lwip-promise module is in order, which will wrap the original
lwip module with support for promises.
Also worth checking Bluebird's PromisifyAll
https://github.com/petkaantonov/bluebird/blob/master/API.md#promisepromisifyallobject-target--object-options---object
.

Something like this would be nice:

lwip.open('image.jpg')
.then(function(image){
return image.scale(0.5);
})
.then(function(image){
return image.rotate(45);
})
.catch(function(err){
// ...
});

I'm open for discussion on what's the best approach.
If anybody else would like support for promises please let me know here.

Thanks.

—
Reply to this email directly or view it on GitHub
#63 (comment).

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+1, I would really like to see a promises implementation

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I have tried to use promisifyAll from Bluebird to use promises on lwip but unfortunately it throughs error and I can't use it.

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I just tried the following but can't get further.

var lwip = Promise.promisifyAll(require('lwip'));
Promise.promisifyAll(require('lwip/lib/Image').prototype);

lwip.openAsync(buf, 'png').then(function(image) {
  image.toBufferAsync('gif').then(function(buffer) {
    console.log(buffer);
  });
})

Edit: updated with fixed code, I had the arguments wrong!

bluebird 2.4.2
lwip 0.0.6 branch

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@raine great, looks good!

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Working example:

var lwip = Promise.promisifyAll(require('lwip'));
Promise.promisifyAll(require('lwip/lib/Image').prototype);
Promise.promisifyAll(require('lwip/lib/Batch').prototype);

lwip.openAsync('image.jpg')
  .then(function(image) {
    return image.batch()
      .rotate(45, 'white')
      .scale(0.5)
      .blur(5)
      .writeFileAsync('output.jpg');
  })
  .catch(function(err) {
    console.log('something went wrong', err);
  });

Another example without batch():

lwip.openAsync('image.jpg')
  .call('rotateAsync', 45)
  .call('scaleAsync', 0.5)
  .call('writeFileAsync', 'output.jpg')
  .catch(function(err) {
    console.log('something went wrong', err);
  });

Hope this helps.

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Without modifying the core library, I've used https://github.com/then/promise successfully to promisify multiple lwip image processing steps. Would be happy to create a Gist if there's any interest.

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I've created package that implements this issue: https://github.com/nkt/node-lwip-promise.
It's successfully works in production right now. Thanks!

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That would indeed be a very nice feature. The future is definitely moving towards promises, as they drive ES7 async/await functions, which you can use today with babel or co. I'm against wrapper modules because they might not be always up-to-date, so promisifyAll for now, but that Async suffix and the boilerplate is annoying.

This is an example taken from a tutorial from http://thejackalofjavascript.com/image-manipulation-node-js/ for a simple image manipulation. Look at the callback hell:

var lwip = require('lwip');

var lefty, righty;

lwip.open('images/portrait.jpg', function(err, image) {
  var imgWidth = image.width(),
    imgHeight = image.height();

  image.crop(0, 0, (imgWidth / 2) - 1, imgHeight - 1, function(err, cropped) {
    lefty = cropped;
    lefty.writeFile('images/processed/portrait_lefty.jpg', function(err) {
      if (err) throw err;

      // re-opening the same image, coz the `image` is == `cropped`
      // If we do not get a fresh copy, we will be modifing the cropped image :(

      lwip.open('images/portrait.jpg', function(err, image) {
        if (err) throw err;

        var imgWidth = image.width(),
          imgHeight = image.height();

        image.crop(imgWidth / 2, 0, imgWidth - 1, imgHeight - 1, function(err, cropped) {
          if (err) throw err;

          righty = cropped;

          righty.writeFile('images/processed/portrait_righty.jpg', function(err) {
            if (err) throw err;

            lwip.create(imgWidth, imgHeight, 'white', function(err, newImg) {
              if (err) throw err;

              newImg.paste(0, 0, righty, function(err, newImg) {
                if (err) throw err;

                newImg.paste(imgWidth / 2, 0, lefty, function(err, newImg) {
                  if (err) throw err;

                  newImg.border(18, 'gray', function(err, newImg) {
                    if (err) throw err;

                    newImg.writeFile('images/processed/portrait_new.jpg', function(err) {
                      if (err) throw err;
                    }); // write the final output

                  }); // add a border - for fun \O/

                }); // paste lefty to the right part of the new image 

              }); // paste righty to the left part of the new image

            }); // create a blank image

          }); // write righty to file for reference

        }); // righty creation

      }); // re-open the same image

    }); // write lefty to file for reference

  }); // lefty creation
});

With promises or async/await that would be so much better.

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Maybe we can add @raine's working example to readme?

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@EyalAr
I seem to be unable to do any kind of promisification of LWIP due to decree. While using a promisified form of the open function, I get this error:

Error: Unknown arguments configuration,images/myimg.png

Is there any way I can still use promises with LWIP?

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@RobertHerhold this works for me:

const lwip = require('lwip')
Promise.promisifyAll(lwip)
Promise.promisifyAll(require('lwip/lib/Image').prototype)
Promise.promisifyAll(require('lwip/lib/Batch').prototype)

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@felixfbecker Thanks for the quick response. Turns out my issue was more of a poor understanding of LWIP's API than anything.

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@felixfbecker Ran into another issue. I have the following code:

return lwip.openAsync(inname)
      .then(image => image.batch().resize(size, size, "nearest-neighbor").toBufferAsync('png'));

and I get this error:

Unhandled rejection Error: Unknown arguments configuration,200,200,nearest-neighbor

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@RobertHerhold that has nothing to do with promises, please ask this on stackoverflow

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setPixel seems to be asynchronous. I want to draw a PNG from scratch and know when it is done. Would be great to be able to use Promise.all() for this.

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