Converting images to webp or jpeg2000 in Pythonista

[Niklas]

Thank you, I will try to make that work! 🙂

Best regards, Niklas

[mikael]

@Niklas, unfortunately it looks like the version of PIL included with Pythonista is too old to recognize .webp, and not compiled with j2k support.

I tested with:

import photos

photo = photos.get_assets()[-1].get_image()

photo.save('test.j2k')

[mikael]

@Niklas, iOS Safari supports webp since iOS 14, so conversion should be possible in a WebView via JavaScript. Relevant-looking js sample here.

And Apple Shortcuts supports image conversion to JPEG2000, so you might be able to do everything there, or branch out to run just the conversion in Shortcuts.

[Niklas]

Thank you, @mikael, doing it in Shortcuts worked perfectly! 🙂 Like you, I tested different ways of making it work in Pythonista, but gave up. If someone else needs it, the shortcuts is here:

https://www.icloud.com/shortcuts/de01f3230990494b85129535fa855d5d

You can pick images from Photos or Files and it converts them to jpeg2000. Then you can save them back to Photos or Files.

Hopefully it will be possible to do this in Pythonista eventually. 🙂

[cvp]

@Niklas I think that it could be possible that
In Pythonista

• you ask/get the image
• you save the file in Files (in an external folder)
• you start a shortcut which
  In your shortcut
• you get the file from Files
• you convert to jpeg2000
• you save in Files
• you start Pythonista script
  In Pythonista
• you get the converted file
• ...

Édit: sorry, if it was what you want to say by "Hopefully it will be possible to do this in Pythonista eventually."

[Niklas]

Thank you! I’m thinking of doing something like that, but more or less only do the .jp2 conversion in Shortcuts and everything else in Pythonista. 🙂

What I meant by the sentence you quoted, is that I hope Pythonista will get built-in support for webp and jpeg2000 conversions in the future. Since that is what Google recommends if you want high website rankings in their search results, I think Pythonista would be a good place to have it on iPad.

[JonB]

I believe that CGCreateDestination supports writing to j2k.

https://stackoverflow.com/questions/19749482/how-do-i-convert-uiimage-to-j2k-jpeg2000-in-ios

[Niklas]

I tried to read and follow what they did there, but it was above my knowledge level. Thanks anyway! 🙂

[Niklas]

A related question:

If I get a jp2 image from Shortcuts via the clipboard, can I save it to Files in Pythonista? When I try to do it with image.save(image-to-save) I get an OSError: encoder jpeg2k not available, which I can understand. I think there should be a way to disregard the file type and save it the way it came, without making any changes other than the file name.

Is this possible?

[cvp]

@Niklas why are you passing the image file as an image ? In shortcuts, you could save it in Files.

Édit: what do you want to do with this image in Pythonista?

[mikael]

@Niklas, PIL images have the tobytes method that could possibly do the trick, but see the warning in doc.

Probably better to save in Files, as @cvp suggested, and just pass the path. Then you can handle it in Pythonista like any other binary file.

[Niklas]

@cvp, my intention was to do as much as possible in Pythonista, since I find Shortcuts so slow. Your question got me to think and I went with your suggestion instead. 🙂 Also, I already had a shortcut that did most of what I wanted.

@mikael, thanks for suggesting tobytes. I will try to keep that in mind for another time. 🙂

[cvp]

@Niklas I've tried during some hours to convert @JonB 's idea into Pythonista, but without any success. Sorry

[mikael]

@cvp, want to share the code for some joint debugging?

[cvp]

@mikael I think it is far from my skills

'''
https://stackoverflow.com/questions/19749482/how-do-i-convert-uiimage-to-j2k-jpeg2000-in-ios

#import <ImageIO/ImageIO.h> // or @import ImageIO if modules enabled
#import <MobileCoreServices/MobileCoreServices.h>

// ...    

// quality is 0-1 (0 = smallest file size, 1 = lossless quality)
+ (NSData*) convertToJPEG2000:(UIImage*)image withQuality:(float)quality
{
    NSMutableData* d = [NSMutableData data];
    CGImageDestinationRef destinationRef = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)d, kUTTypeJPEG2000, 1, NULL);
    CGImageDestinationSetProperties(destinationRef, NULL);
    CGImageDestinationAddImage(destinationRef, image.CGImage, (__bridge CFDictionaryRef)@{ (NSString*)kCGImageDestinationLossyCompressionQuality: @(quality) });

    if (!CGImageDestinationFinalize(destinationRef))
    {
        d = nil;
    }
    CFRelease(destinationRef);

    return d;
}
'''
from   objc_util import *
import time
import ui

d = NSMutableData

CGImageDestinationCreateWithData = c.CGImageDestinationCreateWithData
CGImageDestinationCreateWithData.restype = c_void_p
CGImageDestinationCreateWithData.argtypes = [c_void_p, c_void_p, c_void_p, c_void_p]

kUTTypeJPEG2000 = 'public.jpeg-2000'	# UTI for a Jpeg2000

imagedest = CGImageDestinationCreateWithData(d, kUTTypeJPEG2000, 1, None)

CGImageDestinationSetProperties = c.CGImageDestinationSetProperties
CGImageDestinationSetProperties.restype = None
CGImageDestinationSetProperties.argtypes = [c_void_p, c_void_p]
CGImageDestinationSetProperties(d, None)

img = ui.Image.named('test:Peppers').with_rendering_mode(ui.RENDERING_MODE_ORIGINAL).objc_instance

CGImageDestinationAddImage = c.CGImageDestinationAddImage
CGImageDestinationAddImage.restype = None
CGImageDestinationAddImage.argtypes = [c_void_p, c_void_p, c_void_p]
CGImageDestinationAddImage(d, img, None)# {ns('kCGImageDestinationLossyCompressionQuality'):1})
time.sleep(3)

CFRelease = c.CFRelease
CFRelease.restype = None
CFRelease.argtypes = [c_void_p]
CFRelease(d)

[mikael]

@cvp, yeah, it looked more challenging than usual. Would it matter if you objc_util.load_framework('ImageIO') or not?

[cvp]

@mikael sincerely, I don't know, I have stopped to spend time with this test.

[JonB]

You were really close! CGDestnationXXX() takes imagedest as first param. ine of the signatures was wrong (needed a size_t), and the kUTType ought to be an nsstring.

This seems to work!
(edit: refactored into a convienent function)
(edit again, fixed a typo, added quality)

'''
https://stackoverflow.com/questions/19749482/how-do-i-convert-uiimage-to-j2k-jpeg2000-in-ios

#import <ImageIO/ImageIO.h> // or @import ImageIO if modules enabled
#import <MobileCoreServices/MobileCoreServices.h>

// ...    

// quality is 0-1 (0 = smallest file size, 1 = lossless quality)
+ (NSData*) convertToJPEG2000:(UIImage*)image withQuality:(float)quality
{
    NSMutableData* d = [NSMutableData data];
    CGImageDestinationRef destinationRef = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)d, kUTTypeJPEG2000, 1, NULL);
    CGImageDestinationSetProperties(destinationRef, NULL);
    CGImageDestinationAddImage(destinationRef, image.CGImage, (__bridge CFDictionaryRef)@{ (NSString*)kCGImageDestinationLossyCompressionQuality: @(quality) });

    if (!CGImageDestinationFinalize(destinationRef))
    {
        d = nil;
    }
    CFRelease(destinationRef);

    return d;
}
'''
from   objc_util import *
import ctypes
import time
import ui
load_framework('ImageIO')

CGImageDestinationCreateWithData = c.CGImageDestinationCreateWithData
CGImageDestinationCreateWithData.restype = c_void_p
CGImageDestinationCreateWithData.argtypes = [c_void_p, c_void_p, ctypes.c_size_t, c_void_p]

CGImageDestinationSetProperties = c.CGImageDestinationSetProperties
CGImageDestinationSetProperties.restype = None
CGImageDestinationSetProperties.argtypes = [c_void_p, c_void_p]

CGImageDestinationAddImage = c.CGImageDestinationAddImage
CGImageDestinationAddImage.restype = None
CGImageDestinationAddImage.argtypes = [c_void_p, c_void_p, c_void_p]

CGImageDestinationFinalize=c.CGImageDestinationFinalize
CGImageDestinationFinalize.restype=ctypes.c_int
CGImageDestinationFinalize.argtypes=[c_void_p]

CFRelease = c.CFRelease
CFRelease.restype = None
CFRelease.argtypes = [c_void_p]

kUTTypeJPEG2000 =  c_void_p.in_dll(c,'kUTTypeJPEG2000')    # UTI for a Jpeg2000
kCGImageDestinationLossyCompressionQuality=c_void_p.in_dll(c,'kCGImageDestinationLossyCompressionQuality')

'''def convert_image_to_jpeg2000(uiimg, out_filename, quality=1):
	uiimage=ui.Image
	out_filename=str
	quality: 0=smallest, 1=lossless'''
def convert_image_to_jpeg2000(uiimg, out_filename, quality=1):
	d = NSMutableData.new()
	imagedest = CGImageDestinationCreateWithData(d, kUTTypeJPEG2000, 1, None)

	CGImageDestinationSetProperties(imagedest, None)

	#img = ui.Image.named('test:Peppers').with_rendering_mode(ui.RENDERING_MODE_ORIGINAL).objc_instance

	CGImageDestinationAddImage(imagedest, uiimg.objc_instance.CGImage(),ns({'kCGImageDestinationLossyCompressionQuality':quality}))

	if not CGImageDestinationFinalize(imagedest):
		raise Exception('Image Conversion Failed')
	CFRelease(imagedest)

	with open(out_filename,'wb') as f:
		f.write(nsdata_to_bytes(d))

if __name__=='__main__': 		
	img=ui.Image.named('test:Lenna')
	convert_image_to_jpeg2000(img, 'lenna.j2k',0)

	import console
	console.quicklook('lenna.j2k')
	print('success!' )
	

[cvp]

@JonB You're really the champion. Where could go this forum without you?
Thanks for everybody.
Sincerely, I don't know why I have even tried.

[JonB]

@cvp You did the heavy lifting . A minor update above adds the quality parameter (at quality=1, lenna is 445kB. at 0, it is 3kB...