Clarify meaning of image resolution

Author: JorjMcKie

docs/page.rst

@@ -1705,8 +1705,8 @@ In a nutshell, this is what you can do with PyMuPDF:
          height          original image height (``int``)
          cs-name         colorspace name (``str``)
          colorspace      colorspace.n (``int``)
-         xres            resolution in x-direction (``int``)
-         yres            resolution in y-direction (``int``)
+         xres            resolution in x-direction (``int``) [#f10]_
+         yres            resolution in y-direction (``int``) [#f10]_
          bpc             bits per component (``int``)
          size            storage occupied by image (``int``)
          digest          MD5 hashcode (``bytes``), if ``hashes`` is true
@@ -2360,4 +2360,6 @@ The page number "pno" is a 0-based integer `-∞ < pno < page_count`.
 
 .. [#f9] Objects inside the source page, like images, text or drawings, are never aware of whether their owning page now is under OC control inside the target PDF. If source page objects are OC-controlled in the source PDF, then this will not be retained on the target: they will become unconditionally visible.
 
+.. [#f10] This value is always 96, the default of the PDF interpreter. It **does not reflect** the resolution of the image itself. If you need the image's resolution, use the :meth:`Pixmap.xres` and :meth:`Pixmap.yres` attributes of the :ref:`Pixmap` created from the image binary.
+
 .. include:: footer.rst

docs/textpage.rst

@@ -214,8 +214,8 @@ ext             image type (``str``), as file extension, see below
 width           original image width (``int``)
 height          original image height (``int``)
 colorspace      colorspace component count (``int``)
-xres            resolution in x-direction (``int``)
-yres            resolution in y-direction (``int``)
+xres            resolution in x-direction (``int``) [#f3]_
+yres            resolution in y-direction (``int``) [#f3]_
 bpc             bits per component (``int``)
 transform       matrix transforming image rect to bbox (:data:`matrix_like`)
 size            size of the image in bytes (``int``)
@@ -388,4 +388,6 @@ This image shows the relationship between a character's bbox and its quad: |text
 
 .. [#f2] The coordinate systems of MuPDF and PDF are different in that MuPDF uses the page's top-left point as `(0, 0)`. In PDF, this is the bottom-left point. Therefore, the positive direction for MuPDF's y-axis is **from top to bottom**. This causes the sign change for the sine value here: a **negative** value indicates anti-clockwise rotation of the text.
 
+.. [#f3] This value is always 96, the default of the PDF interpreter. It **does not reflect** the resolution of the image itself. If you need the image's resolution, use the :meth:`Pixmap.xres` and :meth:`Pixmap.yres` attributes of the :ref:`Pixmap` created from the returned image binary.
+
 .. include:: footer.rst