Add JPEG quality option

[timomeara]

something like this would be great:
'large': {'width': 354, 'height':270, 'crop':True, 'resample':True, 'jpg_quality':75}

[timomeara]

#187

i hope this is better.

[codingjoe]

@timomeara really appreciated your effort here, I just don't want to rush this. I agree that JPEG is probably the most likely of files this library supports.

I think this could go two different ways. Ether you have attributes per mime type

img = stdimage.StdImageField(variations={}, jpeg_attrs={}, png_attrs={})

or
have a subclass of the field that is JPEG only.

Both solutions have their pros and cons I guess. Maybe there is also a third one. Let me know what you think.

[timomeara]

hey-
np. we are going to use this in an app that goes live 4/1 so i'm motivated ;)

i'm not sure i understand the problems with either of the approaches i've submitted.

i get the png does not support the quality param... but it just ignores it... it's a little ambiguous, but it won't break anything.

a jpg_quality attrib is less ambiguous but that didn't fly either ;)

what other attribs would you put in the png{} ?

i'm setting optimize=True on everything, but i think that's what you were doing too, no?

tmo

[codingjoe]

ok, here is what I would recommend to do. I would create a subclass, a JPEG field that always saves the variations as JPEG. For this field you can of course add attributes that are JPEG specific.

[codingjoe]

Please don't be discouraged. I do see the need for this feature. I am just very careful with adding new features, since I have to maintain them ;)

[codingjoe]

to be a bit more precise what I am suggesting is:

class JpegImageField(StdImageField):
    """Do whatever you want."""
    pass

[marojenka]

hi,
rendering (some) variations as jpeg would be really nice option I believe. Page full of png thumbnails makes me sad. Clearly it's additional hassle to maintain, so it's up to you to decide.
Defining own class is not a big deal, sure, and I might be missing something but the only way to mess with saving variations is to hack render_variation method which is not really friendly due to it's size.
As for now I copy whole function to my custom class if I need it.

[codingjoe]

I agree fully. I am just waiting for someone to submit a patch ;)

[marojenka]

@codingjoe well this is how I see it:
#188

[marojenka]

After pull #188 I use something like this to force all variations to be JPEGs.

    @classmethod
    def process_variation(cls, variation, image):
        img, kargs = super().process_variation(variation, image)
        img = img.convert('RGB')
        kargs['format'] = 'JPEG'
        return (img, kargs)

    @classmethod
    def get_variation_name(cls, file_name, variation_name):
        std_name = super().get_variation_name(file_name, variation_name)
        path, _ = os.path.splitext(std_name)
        return path + '.jpeg'

By the look of it I think may be actual resampling also should be separate function.

[codingjoe]

There is a JPEGField now, I would be open to adding a quality arguments to that.