JPEG writing with coefficients and quantization matrix

[ehgusehgus]

Is there a function that save jpeg file with the DCT coefficients and quantization matrix directly?(not with the pixel values)

Thank you for reading

[dwgoon]

You can use write method as follows

import jpegio as jio

jpeg = jio.read("image.jpg")
# Modifying jpeg.coef_arrays...
# Modifying jpeg.quant_tables...
jio.write(jpeg, "image_modified.jpg")

[ehgusehgus]

jpegio.write() function seems to cause error.

Traceback (most recent call last): File "", line 1, in File "C:\Users\ehgus\Anaconda3\lib\site-packages\jpegio-0.2.1-py3.6-win-amd64.egg\jpegio\io.py", line 20, in write obj.write(fpath) File "jpegio\decompressedjpeg.pyx", line 195, in jpegio.decompressedjpeg.DecompressedJpeg.write File "jpegio\decompressedjpeg.pyx", line 196, in jpegio.decompressedjpeg.DecompressedJpeg.write File "jpegio\decompressedjpeg.pyx", line 200, in jpegio.decompressedjpeg.DecompressedJpeg._write_markers TypeError: object of type 'NoneType' has no len()

And also something like

jpeg = jio.read("image.jpg") jpeg.write("image_modified.jpg")

does not saving the modified coefficients. It saves with original one.

[dwgoon]

Refer to the code snippet again, and correct your code as follows, please.

jio.write(jpeg, "image_modified.jpg")

[ehgusehgus]

Yes. I've tried like this.

import jpegio
c = jpegio.read('input.jpg')
jpegio.write(c,'image_modified.jpg')

But it produces error like below.

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\ehgus\Anaconda3\lib\site-packages\jpegio-0.2.1-py3.6-win-amd64.egg\jpegio\io.py", line 20, in write
    obj.write(fpath)
  File "jpegio\decompressedjpeg.pyx", line 195, in jpegio.decompressedjpeg.DecompressedJpeg.write
  File "jpegio\decompressedjpeg.pyx", line 196, in jpegio.decompressedjpeg.DecompressedJpeg.write
  File "jpegio\decompressedjpeg.pyx", line 200, in jpegio.decompressedjpeg.DecompressedJpeg._write_markers
TypeError: object of type 'NoneType' has no len()

I think this error is caused by creating empty new object in the writing function and try to save that object.

And if I try the writing like

jpeg = jpegio.read("image.jpg")
jpeg.write("image_modified.jpg")

It does not save the modified coefficient but save the original one

[dwgoon]

Thanks for giving me the hint. I've fixed jpegio.write following your comment. Test the revised code, please.