2008.02.11 07:43 "[Tiff] TIFFReadRGBAImage rendering upside-down", by Mick O'Neill

2008.02.11 17:20 "RE: [Tiff] Re: Help with TIFFWriteScanline()", by Chris Cox

I think you're confusing SamplesPerPixel with BitsPerSample.

-----Original Message-----

From: tiff-bounces@lists.maptools.org on behalf of James Sumners Sent: Mon 2/11/2008 8:33 AM

To: tiff@lists.maptools.org

Subject: [Tiff] Re: Help with TIFFWriteScanline()

After browsing the mailing list archives I found out about the tiffinfo tool. tiffinfo reported that my original image had a SamplesPerPixel of 1. For some reason, unbeknownst to me, my program is getting a value of 0 for SamplesPerPixel from the original image. So I manually set the value to 8, because that is what I understand the specification to be (8 or 16 SPP for grayscale/color and 1 SPP for bilevel). After changing my manual SPP value from 8 to 1 the copied image is written correctly.

This is the first time I've done any graphics programming. So I'm sure that I am not understanding something. Would someone please explain this situation to me? Would 8 SPP squeeze the image into a smaller space? How is 1 SPP producing a grayscale image?

On Feb 11, 2008 10:52 AM, James Sumners <james.sumners@gmail.com> wrote: > I've written a program[1] that reads a grayscale image into memory and > writes it to another file. The problem is that the new image is

> multiple copies of the original image in the same pixel space. It's a > bit difficult to describe. Included in the zip is "fractal_gs.tiff",

> the original image, and "fractal_gs_2.tiff", the copy.


> If I try to write the new image with TIFFWriteRawStrip() I get append > errors. Using TIFFWriteScanline() I get an image, just not the one I

> expect. What am I doing wrong?
> [1] -- http://student.claytonstate.net/~jsumners/files/tiff_copy.zip

James Sumners

"All governments suffer a recurring problem: Power attracts pathological personalities. It is not that power corrupts but that it is magnetic to the corruptible. Such people have a tendency to become drunk on violence, a condition to which they are quickly addicted."

Missionaria Protectiva, Text QIV (decto)

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