corrupt image

[JoeB]

Like Kathy_9, I opened your image in X7 and it was corrupted. So then I opened it in Photoshop CS6 where it opened fine, and then saved it as a TIF file with a different name so as not to overwrite the original. That file I saved using PS now opens properly in PSPX7. I suspect the corruption is the result of some bad information in the tif header from the scan that confuses PSP but not other image editors or readers, but don't really have a clue.

Two things of note that maybe others can answer. First, I saved it with PS using LZW compression, and the saved file was 44MB, about half the size of the original. Then I did another save of the original but chose the None option in the compression dialogue and saved that. It's file size was only 37MB, which was even smaller than using LZW compression (although it also opens in PSPX7). Anybody have any idea why NONE for compression in PS resulted in a smaller file size than LZW compression?

[photodrawken]

Two things of note that maybe others can answer. First, I saved it with PS using LZW compression, and the saved file was 44MB, about half the size of the original. Then I did another save of the original but chose the None option in the compression dialogue and saved that. It's file size was only 37MB, which was even smaller than using LZW compression (although it also opens in PSPX7). Anybody have any idea why NONE for compression in PS resulted in a smaller file size than LZW compression?

I don't know why the LZW compressed file is larger than the uncompressed file, but that has apparently been a well-known fact for the past 30 years. If you search the Web for "TIF compression" and "LZW compression", you'll find lots of articles that mention that LZW compressed 16-bit TIF images are larger than the uncompressed images.

The documentation that describes the algorithms behind LZW compression and decompression cause my eyes to very quickly glaze over , but it seems that whenever the algorithms encounter data that is only slightly different than data already encoded (compressed), the algorithms are forced to create additional new large encoding tables. Don't quote me on that, however.

The bottom line is that compressing TIF images with LZW works best with images having a lot of repetitive (redundant) data. In other words, monochrome images or images with large areas of grey compress nicely. Images with a lot of data that is unique will not compress well, and will actually take up more space than uncompressed images. By its very nature, a 16-bit image contains a hell of a lot more pixels that are unique than does an 8-bit image, so a 16-bit LZW TIF image will necessarily be larger than the uncompressed original image.

[hartpaul]

Well I did some tests with earlier versions of PSP.
That Tif was 90858 Kb and opened to provide two "duplicate" images in PSP8, X2 and X3.
It showed as two corrupted files in X4-X9.
I resaved the two identical ??? files as uncompressed tifs from PSPX2 and they were :
scan0017 1 at 42591KB
and
scan0017 2 at 42047 KB

So it seems that again in the changeover from Jasc based coding to Corel based coding some problems have arisen in reading some files.

[fndooley]

Thanks Kathy. Maybe I can open it up in there and save it under a different file name then try to reopen it in Corel. More of a mystery that I want to solve now than anything else.

[JoeB]

First, @hartpaul was likely on the mark (partially, at least when it comes to the image the OP posted) when he said that Corel coding likely changed the way PSP reads this particular type of .tif file starting from version X4, because the posted image opens fine in previous versions.

I opened the .tif in Irfanview (excellent free program) and checked the image information (screenshots attached). The Information dialogue on the left of the image I have attached tells the tale. It shows that this .tif file is a 2 page .tif. That screenshot is of the first page, and the information screenshot on the right is the image information the second page. The second page is almost identical to the first, except that it is slightly smaller in width pixel size, explaining the difference in file sizes when each of the two pages is saved separately.

The reason that we get different results when opening the image in different viewers/editors is simply because of the support - or lack thereof - that these different programs have for multipage .tif images. Some programs (like Photoshop) do not support them well and so only open the first page. Some (like Paintshop Pro and Irfanview) actually do support multipage .tif files, even up to PSP version X9 - I tried it with a 10 page .tif in and that file opened as 10 good images. So that explains why some programs only open one image and others open the multiple images in the file

So why do later versions of PSP open the two images in the OP's file but show them as corrupt? I can only speculate based on very limited knowledge. The 10 page .tif file that opens all pages fine in all PSP versions have each image page exactly the same pixel size. As previously stated, that is not the case with the OP's image. So perhaps a slight coding change in later versions was sufficient to cause PSP to recognize the multiple pages but not able to properly interpret the image tag information of this particular image or maybe any multipage .tif where the pixel sizes of the pages are not identical. Just my guess.

And, for all I know, perhaps all images in a multipage .tif are supposed to have the same pixel dimensions and, in the case of this image, the person who created the image did something wrong, resulting in the second page image being the wrong dimension, and maybe the file is, indeed, corrupt but still interpretable by some programs.

[fndooley]

JoeB - wanted to get on and thank you for your in-depth reply. To be honest, had to read it a couple of times. You obviously know your stuff. Any idea how I can format the picture in a way to maintain as much detail as possible and still be able to edit it here? Is there any way to convert it back to a single image or is that a stupid question?

[JoeB]

JoeB - wanted to get on and thank you for your in-depth reply. To be honest, had to read it a couple of times. You obviously know your stuff. Any idea how I can format the picture in a way to maintain as much detail as possible and still be able to edit it here? Is there any way to convert it back to a single image or is that a stupid question?

No question is a stupid question! It's not asking at all that, for all of us, is likely not the best approach to any issue.

As to your question here, I don't think it's really a problem for you. First, no, I don't think there is a way to keep the two pages and make them one good page, but I don't see any reason for doing so. A two page (or multipage) tif image just means that it has more than one image stored in that original image, sort of like layers but they are all separate images and usually each page is a different image. It's just a way of storing lots of different images in one .tif image file. In this one that you posted it's just that both pages are of the same image, just slightly different sizes. So you don't need both pages to edit, just the first page/image.

As has been pointed out by me and others, the image can be opened by various programs. Some, like Photoshop, open only the first page, and that can be saved as a .tif image and then you can edit that in PSP. My testing shows that saving it as uncompressed .tif in Photoshop keeps the original file size (approx. 43mb) of that first page of the image that Photoshop opens.

The free program like Irfanview, which opens both pages as separate image pages. opens the first (larger) page first and will save as a .tif image but seems to compress it regardless of which .tif option you choose, and you end up with an image only about 17mb file size, which means some data has been lost even if you can't see it visually.

Perhaps another free program that others have mentioned (or a trial of Photoshop or another paid program) can save that first page of the image in its original 43mb file size when saving as .tif. The chances are that most programs that do open both pages of this image will open the first page first and likely open both with a sequential number so that you'll know which is the first page and which is the second. The first page is the one you want, being the larger of the two.

In all of the above cases, the image you save as .tif with those other programs will then be editable in PSP.

So what program you use to save a copy of the first page of the original image as a .tif file depends on how serious you are about the quality of the saved file when you start your editing of it in PSP. With the Photoshop saved copy (or any other program that will save that first page image as .tif at close to 43mb file size) you'll be starting with the best quality. But, depending on what you need the final result for, the other programs might give you a copy that works just fine.

Sorry you had to read my previous post a few times to get it. Maybe I need to learn to explain my thoughts better. )

[fndooley]

you explain great JoeB and I REALLY appreciate you taking the time to walk me through this. Have learned a lot. Hats off. I did open it in Infanview and saw the exact results you described. Will check around for another acceptable program, either free or trial. Scanned this image from a slide, so I can always go back and rescan it too. Not sure why it saved it this way, but moving on with my life. Thanks again. Owe ya one.
Fred