Image metadata is not stored within the encoded images of a PDF. If metadata is stored at all, it is stored in PDF itself, but stripped from the underlying image. The metadata you see in your example is likely all that you'll be able to get. It's possible that PDF encoders may store image metadata elsewhere in the PDF, but I haven't seen this. (Note this metadata question was also asked for Java.)

It's definitely possible to extract the stream however, as you mentioned, you use the getData operation.

As for replacing it, you'll need to create a new image object with the PDF, add it to the end, and update the indirect Object pointers accordingly. It will be difficult to do this with PyPdf2.

PyPDF2 can extract all images from a PDF.

PyPDF2 currently cannot render the page to an image.

Anyway, how can I crop part of PDF; page width and 100 pixels down from top in PyPDF2?

You can change the cropbox of a page: https://pypdf2.readthedocs.io/en/latest/user/cropping-and-transforming.html

cropbox = page.cropbox
page.cropbox = RectangleObject([cropbox.left, cropbox.bottom, cropbox.right - 100, cropbox.top - 100])

However, if I remember it correctly, the unit is not (necessarily) in pixels. I would need to look that up in the specs.

You can use the module PyMuPDF. This outputs all images as .png files, but worked out of the box and is fast.

import fitz
doc = fitz.open("file.pdf")
for i in range(len(doc)):
    for img in doc.getPageImageList(i):
        xref = img[0]
        pix = fitz.Pixmap(doc, xref)
        if pix.n < 5:       # this is GRAY or RGB
            pix.writePNG("p%s-%s.png" % (i, xref))
        else:               # CMYK: convert to RGB first
            pix1 = fitz.Pixmap(fitz.csRGB, pix)
            pix1.writePNG("p%s-%s.png" % (i, xref))
            pix1 = None
        pix = None

see here for more resources

Here is a modified the version for fitz 1.19.6:

import os
import fitz  # pip install --upgrade pip; pip install --upgrade pymupdf
from tqdm import tqdm # pip install tqdm

workdir = "your_folder"

for each_path in os.listdir(workdir):
    if ".pdf" in each_path:
        doc = fitz.Document((os.path.join(workdir, each_path)))

        for i in tqdm(range(len(doc)), desc="pages"):
            for img in tqdm(doc.get_page_images(i), desc="page_images"):
                xref = img[0]
                image = doc.extract_image(xref)
                pix = fitz.Pixmap(doc, xref)
                pix.save(os.path.join(workdir, "%s_p%s-%s.png" % (each_path[:-4], i, xref)))
                
print("Done!")