ImageUtils.getDataURL: Added warning when saving image as jpg.

[mrdoob]

Description

Log a warning when converting a image to jpeg due to its dimensions.
Seems like I forgot what issue/pr discussed this a few days ago. @Mugen87 do you remember?

[Mugen87]

Seems like I forgot what issue/pr discussed this a few days ago. @Mugen87 do you remember?

No sorry. But the warning does make sense.

[gsimone]

Hey 👋 I just stumbled onto this, should we think about making this optimization skippable?

This lets users select the output format. Of course one can just patch this function away, but it's weird how opinionated the default is – I'm also missing the context here, so forgive me 🙏

getDataURL: function ( image, format ) {

    ...
    if (typeof format === "undefined") {

      if ( canvas.width > 2048 || canvas.height > 2048 ) {

        console.warn( 'THREE.ImageUtils.getDataURL: Image converted to jpg for performance reasons', image );

        return canvas.toDataURL( 'image/jpeg', 0.6 );

      } else {

        return canvas.toDataURL( 'image/png' );

      }
      
    } else {

      if (format === "png") {

         return canvas.toDataURL( 'image/png' );
         
      } else {
        
        return canvas.toDataURL( 'image/jpeg', 0.6 );
        
      }
  }
  ...

}

ADD 1: Also the fact that jpeg is always saved with quality 0.6, we could even expose toDataUrl arguments like this:

(from https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toDataURL )

getDataURL(image, type, encoderOptions) {
  ...
}

This could also be reflect in Texture.toJSON, with additional type and encoderOptions arguments to allow more control to users

[mrdoob]

@gsimone do you mind detailing a bit what your use case is?

[gsimone]

We use Texture.toJson to serialize user-uploaded textures that might exceed 2048x2048, so a user uploaded a transparent png that was like 5k * 1k and it lost alpha information when it was serialized. We can of course work around this, but it's something that people might stumble into, might be worth at least documenting — although I'm still not sure why it's necessary