Jpeg Image Quality about sharp

[pierreinglebert]

It's hard coded here https://github.com/lovell/sharp/blob/master/src/sharp.cc#L262 and https://github.com/lovell/sharp/blob/master/src/sharp.cc#L277

[lovell]

Hi @KevinJaspal, thanks for the kind words.

As @pierreinglebert says, JPEG quality is currently fixed at 80%. If it's good enough for Wikipedia then its good enough for us 😄

More seriously, I'd be happy to expose quality as an optional setting in the range 1-100, with a sensible default (perhaps the current value of 80 for backwards compatibility).

This option would apply to the lossy formats of JPEG, WebP and TIFF (uses JPEG under the hood).

For the lossless PNG format, accepting an optional compression value makes more sense as the underlying zlib library takes an compression value of between -1 and 9. (I'm not a fan of the way GraphicsMagick overloads the concept of "quality" to set lossless PNG compression level - the quality remains the same).

[KevinJaspal]

Thanks for the prompt response @pierreinglebert and @lovell :)

I think having a default 80 quality setting with an optional setting that can be specified would be perfect. That way you can maintain backwards compatibility, keep the api simple to use for the majority of users and still provide the flexibility for adjusting the value.

Having an optional compression value for PNG definitely makes more sense than quality.

👍

[lovell]

@KevinJaspal please can you take a look at the API additions on the quality-option branch and let me know if they work for you.

[KevinJaspal]

Hi @lovell

I tried out the quality-option with multiple levels to write a jpeg image, works brilliantly.

Thank you!

[lovell]

No problem, thank you for helping test. This is now merged to master and will be included in v0.4.0.