The Sheriff has been duped by the quacks from World Nut Daily. His case rests largely on those Photoshop layers found in the PDF the White House released. However, as this old video shows, those bizarre layers are just what you get when you scan an old BC and save it as an optimized PDF (you can also read about it here).
In any case, there isn't any point in the WH releasing a materially altered version of the document, since the original remains on file with the Hawaii Department of Health and could be produced if this thing ever comes to a head in court.
On the other hand, releasing a true but suspicion-arousing version (or failing to respond to birther complaints by releasing a 600-dpi flat scan) has the advantage of keeping the whole thing alive. As any well-trained community organizer knows, it helps to keep your opponents looking ridiculous and barking up wrong trees. That's why it took him until last April to release his long form — he only did so when Donald Trump threatened to spread birtherism among independents who might actually be stupid enough to vote for him again. He'll be content to let the issue fester until another Trump comes along. If and when that happens, he knows he can prove what he needs to prove.
B&W:
Bitmap pixelation results from scanning an image in 'B&W' where halftones are not captured; The portions of the image are either black or white with no in between.
Grayscale
Other 'anti-aliased' areas of the birth certificate are a result of a 'grayscale' or 'photograph mode' scan, resulting in halftone shades or GRADUATED TONES.
So, you have a scanned version of 0bama's alleged 'original' birth certificate that includes both of the above conflicting scan types. The ONLY way to explain this is that the certificate itself was modified and constructed using portions from multiple sources (more than just one). The halftone vs. bitmap issue is not a result of OCR either and I do believe Arpaio's Powerpoint presentation explained away your OCR theory too. http://www.youtube.com/watch?v=CGu9NDAw2Vg
Also, there is the problem of 'white clouds' around characters, along with red-shift/blue-shift ghosting too.. Arpaio's team explained these two types of artifacts too and it doesn't bode well for your argument.
Lastly, 0bama's bc is most CERTAINLY NOT A SCAN OF AN ORIGINAL DOCUMENT. It is a DOCUMENT BUILT IN PHOTOSHOP USING AT LEAST TWO SOURCE DOCUMENTS. Enough experts have proven this beyond any shadow of a doubt.
Did you hear about the guy who was present with 0bama at Bill Ayers' mother's house when she introduced 0bama as the 'guy we're trying to get an education for in the United States"??? Sheriff Arpaio's touched upon this at his press conference, so stay tuned..