PyEncoder using self.im.tobytes()

[duaneg3]

I want to have a new encoder which handles ZLIB. The easiest way to do this is to generate a raw stream first and then encode it. When I try to use tobytes() in the encoder it complains:

       def encode(self, bufsize):
           buf1 = self.im.tobytes("raw")

     AttributeError: 'ImagingCore' object has no attribute 'tobytes'

Is there anyway to get this to work??

The work-around seems to be to write a custom _save routine

def _save(im, fp, filename):
    buf1 = im.tobytes()
    buf2 = zlib.compress(buf1);
    fp.write(buf2)

so then can save to an io.BytesIO

        data2 = io.BytesIO()
        img.save(data2,"ZLIB")

However, given I never want to save to a file, this does not seem as clear ..

[radarhere]

buf1 = self.im.tobytes("raw")

The simplest way to do this would be to construct an image around the ImagingCore object.

buf1 = Image.Image()._new(self.im).tobytes("raw")

If you would like to work at a lower level, you could start extracting the code from tobytes() instead.

encoder = Image.core.raw_encoder(self.im.mode, self.im.mode)
encoder.setimage(self.im)
bufsize = max(65536, self.im.size[0] * 4)
bytes_consumed, errcode, data = encoder.encode(bufsize)
if errcode < 0:
	msg = f"encoder error {errcode} in tobytes"
	raise RuntimeError(msg)
buf1 = data

[duaneg3]

This worked very nicely!! Can make a simple ZLIB encoder this way:

class ZLIBEncoder(ImageFile.PyEncoder):
    _pushes_fd = True 
    def encode(self, bufsize):
        buf1 = Image.Image()._new(self.im).tobytes("raw")
        buf2 = zlib.compress(buf1)
        return len(buf2), 1, buf2
Image.register_encoder("ZLIB", ZLIBEncoder)

Can also use the same method to create a JPEG encoder:

class JPEGEncoder(ImageFile.PyEncoder):
    _pushes_fd = True
    def encode(self, bufsize):
        data2 = io.BytesIO()
        Image.Image()._new(self.im).save(data2,'JPEG')
        buf1 = b""+data2.getvalue()
        return len(buf1), 1, buf1
Image.register_encoder("JPEG", JPEGEncoder)