Thanks.
I have done some testing.
Now, I can get the PdfImageObject and add new PdfImageObject.

I have two more questions.

1.
I found that some images in our pdf files are not in the "PageObjects" collection.
I guess it is because the images are not stored at the page level but stored deeper in the hierarchy in form XObjects.
Can PDFium also extract and replace this type of images?

2.
We need to replace the high resolution image in pdf by low resolution image.
I found that "PdfPageObjectsCollection" only have "InsertObject" function.
Can I replace the existing PdfImageObject rather than add a new one?

Hi,

We have some PDFs which have high resolution image (eg 300 dpi).
I need to extract the high resolution images and downsample the images to low resolution images (eg 72 dpi).
Then replace the high resolution image in PDF by the low resolution image.
Can PDFium.NET accomplish this?

Thanks.