unexpected output of make_blob with format keyword if opened by read

[multiSnow]

This is the script:

from wand.image import Image

with Image(filename='test.png',format='PNG') as im:
    print('open by class',im.make_blob(format='RGBA')[:20])

with Image() as im:
    im.read(filename='test.png',format='PNG')
    print('open by read',im.make_blob(format='RGBA')[:20])

generate test.png by this command line:

magick -size 128x128 xc:white test.png

Result of the script:

open by class b'\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff'
open by read b'\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x00\x80'

The 'open by class' is expected.

wand version: 0.6.10
ImageMagick version: 7.1.0-50
system version: Linux 5.19.0-1-amd64 Debian 5.19.6-1

Update:
Remove the 'format' keyword in read() may fix provide expected result, but this keyword is required for loading APNG format using blob or file keyword.

Similar problem also happened with JPEG format, cause the solution in #593 (comment) not work correctly.

Update:
A simpler script to show this problem:

from wand.image import Image

with Image() as im:
    im.read(filename='test.png',format='PNG')
    with im.convert('RGBA') as converted:
        print('before make_blob:',converted.format)
        converted.make_blob()
        print('after make_blob:',converted.format)

[emcconville]

Thanks for reporting this. Looks like something changes in IM-7. I would suspect it's related to the difference between MagickSetFormat vs MagickSetImageFormat. If true, should be a quick fix.

[emcconville]

Possible fix with 7fbf296. Feel free to test it out.

[multiSnow]

Possible fix with 7fbf296. Feel free to test it out.

Confirmed with ImageMagick 7.1.0-50.
Thanks.