About Comparing Drawings or Images
You can compare two drawings or images to show the similarities and differences. In most cases, you can compare any two file formats. However, for PDF and TIFF drawings, you must compare two files of the same format. When you compare drawings or images, you can perform these actions:
• Specify how the drawings or images should be aligned.
• Control whether and how shared and different areas should be displayed.
• Set a value for the threshold that determines which areas of any embedded images are relevant to the comparison.
• Annotate the comparison, and save the annotation set for future use.
On Windows, you can compare drawings saved as PDF files. For the comparison, the PDFs are converted to images in bitmap format, with a default resolution of 300 dots per inch (DPI). For very large files, such as drawings with many sheets, you may choose to decrease calculation time by decreasing the resolution of the images. The temporary bitmap image dimensions are limited to 32,768 x 32,768 pixels. This limitation can result in truncation of the width and/or height for very large drawing sheet dimensions. These issues can be resolved by reducing the image resolution with the environment variable PVIEW_PDFPARSER_DPI. For example, set the following variable to produce images of 150 DPI:
PVIEW_PDFPARSER_DPI=150
The comparison of PDFs is displayed per sheet. As a result, you cannot create an overall report of the changes across sheets. You cannot use this method to compare documents saved as PDFs.
The results of a drawing or image comparison show the areas that are the same, and the areas that are different. In the comparison results view, the two drawings or images are displayed on top of one another, with different colors indicating areas common to both, and those areas unique to each.