Save as JPEG with quality?

[PetrKaleta]

It seems there's no way to set quality when saving jpegs. Which is quite important option, i think. Based on results its default value is 70% which is producing quite bad looking images, especially when processing photos....

[enebo]

Oh yes. Amazing I have not thought of this before. In order to do this the Java APIs need to be capable of it. It would be weird if they did I think but Java can be weird like that...

[PetrKaleta]

Check this out http://www.java2s.com/Code/Java/2D-Graphics-GUI/WritesanimagetoanoutputstreamasaJPEGfileTheJPEGqualitycanbespecifiedinpercent.htm

[PetrKaleta]

Or here http://www.programcreek.com/java-api-examples/index.php?api=java.awt.image.BufferedImage code example 24.

[enebo]

Excellent. This should not be too hard to add.

[PetrKaleta]

Question is, how its on GAE endpoint

[enebo]

Do you need for the GAE backend or are you just trying to be complete. I would hope GAE would also have something for reducing size/quality of jpegs as part of their API.

[PetrKaleta]

Nope, just to be complete... currently I am writing that code, will past awt code here in few mins

[enebo]

https://developers.google.com/appengine/docs/java/javadoc/com/google/appengine/api/images/OutputSettings

[PetrKaleta]

or are you gonna add it? Covering both? Maybe we can call it simply def save_as_jpeg(file, quality) what do you think?

[enebo]

This is a tough question surprisingly. This is a fairly literate API so perhaps .quality(0.75).save which implies needing to save 0.75 as a side-effect so that when save happens it does it's thing. An explicit save like you are saying can also work, but it is more complicated if you factor in with_bytes (and I am unsure if there are any other persisting or data feed variants) as it would also need quality.

If you want to take a crack at this then great. Otherwise I can do it.

[PetrKaleta]

Hmmm, good point with that quality method but I think its a bit above my skills. Right now I am trying to create that custom save_as_jpeg method (as I need it today), but honestly its my first time rewriting this awt code to ruby, so fingers crossed :)

When do you think you can look on it?

[PetrKaleta]

Here is my try, works surprisingly well

class ImageVoodoo
  java_import javax.imageio.ImageIO
  java_import javax.imageio.IIOImage
  java_import javax.imageio.ImageWriteParam
  java_import javax.imageio.stream.FileImageOutputStream

  # Save image as JPEG with given quality
  def save_as_jpg(file, quality)
    fail(ArgumentError, 'Quality out of range') if quality < 0 || quality > 1

    iter = ImageIO.getImageWritersByFormatName('jpg')
    writer = iter.next

    iwp = writer.getDefaultWriteParam
    iwp.setCompressionMode(ImageWriteParam::MODE_EXPLICIT)
    iwp.setCompressionQuality(quality)

    output = FileImageOutputStream.new(JFile.new(file))

    writer.setOutput(output)
    writer.write(nil, IIOImage.new(@src, nil, nil), iwp)

    true
  ensure
    writer.dispose if writer
    output.close if output
  end
end

[enebo]

@PetrKaleta I just landed quality method in commit 2df831a. You can see usage in samples/lossy.rb. Can you do a checkout and see if this is working for you? If so I will spin a release.

[enebo]

Oh also thanks for the snippet. It made adding this functionality much simpler.

[PetrKaleta]

Will test it now, thanks!

btw: you can also mention this quality method in readme sample...

[PetrKaleta]

Works like a charm!

[enebo]

great. I will update example and put out a new release. Thanks for reporting a glaring missing feature.

[enebo]

Released!