The attached PDF file contains a bitonal image which uses the DeviceGray color space, has a BitsPerComponent value of 1, and uses color key masking to make the white pixels transparent (via a Mask array).

The file contains a shipping label with a large X over the entire label, and the text "VOID" over the barcode. One of the lines forming the large X is under the image, and the other is above the image. The "VOID" text is under the label image.

Expected Result: The large X and the "VOID" text are fully visible at any window size, and remain visible both during and after window resize.

Actual Result: When the Acrobat Reader window is larger than a certain size, the image white color mask works correctly and the full X and "VOID" text are visible. But below a certain window size, as the window gets smaller, the full X and the "VOID" text are only visible during the window resize, and become invisible as soon as the window has finished resizing. Please see attached GIF of the window resizing. One of the lines in the X remains visible throughout, because it is not below the image, and thus is not affected by the broken color masking.

Environment: Adobe Acrobat Reader DC 2021.011.20039 on Windows 7