The WH LFBC shows a white border around itself. There are two processes which contributed to this:
- The Xerox WorkCentre applies ‘edge erase’ to remove border marks such as punch holes. This process does not change the size of the image, it merely replaces a border around the image with white pixels.
- Preview adds a clipping mask. A clipping mask does not erase the information but rather hides it. When releasing a clipping mask in Illustrator, the ‘hidden’ information reappears.
Let’s first look at the white border when the clipping mask is removed.
The first problem is that the edge erase comes with presets that can be defined/changed. I have seen references to 0.1” other manuals suggest 0.12” so we may have to infer the settings as done by our friend Vicklund.
Vicklund: Okay, looking at the jpeg in Paint, where I can count pixels and such (lacking a more powerful program), I think I have it figured out. The original image, at 300 dpi, was in landscape and was 3300×2550 (11″x8.5″) [dimensions in pixels unless otherwise noted]. An edge erase border of 36 pixels (.12″) was applied to all borders. Then, the jpeg was compressed. To compress the image via jpeg, the size first was normalized to an 8×8 grid. A 2 pixel border was added to the bottom (left in portrait) and a 4 pixel border was added to the right (bottom in portrait). The image was then compressed to 150 dpi by compressing 16×16 blocks into 8×8 blocks. This works in a top-down flow, so the first 32 pixels at the top (right in portrait) and left (top in portrait) are compressed to 16 pixels and remain white. The remaining four pixels at the top and left are in 8×8 blocks with actual image, so the compression blends them with the colors at the edge. The right (bottom in portrait) compresses from 40 pixels of white border to 20, with no need for blending. Finally, the bottom (left in portrait) 24 pixels remain a 12 pixel white border, while a 14 pixel strip gets blended with a two-pixel strip from the image, creating a weird-looking almost white band that’s 7+1 pixels wide. The bottom and right edges end up being half blocks (8×4 or 4×8), but because they are white, no weird effects are seen.*
As a result, when the 150 jpeg is placed in portrait, there is a white border of 16 at the top and right, 12 at the left, and 20 at the bottom, with an additional blended border of 2 at the top and right, and 7 at the left (with no blending at the bottom).
*A slightly different workflow is that the extra pixels were added at the time of compression from 300 dpi to 150 dpi. These would give 8×8 blocks at the edges that would compress to 4×4 blocks, no trimming needed and the result would look the same. You still need the 16×16 to 8×8 when the large blocks are available to explain the weird bands.
The clipping layer appears to be defined in the Page Setup, which can be accessed through the Page Size setup and can be made default through the “save current settings as default” in the preset drop down. Do we have a way to determine the default settings of the Mac used? Only indirectly.