RE: Graphics Resolution Confusion Once Again

Subject: RE: Graphics Resolution Confusion Once Again
From: Fred Ridder <docudoc -at- hotmail -dot- com>
To: <salt -dot- morton -at- gmail -dot- com>, <techwr-l -at- lists -dot- techwr-l -dot- com>
Date: Tue, 8 Feb 2011 17:11:32 -0500


Sorry, no, the problem is not BMP vs. TIFF. The only file format that would directly affect the final result would be JPEG, since that is an inherently lossy format.

The problem occurs because resizing a raster image by changing the number of pixels is a resampling process, which inevitably causes image degradation regardless of what tool is used. When you're talking about raster images the resolution is actually the number of pixels. For example, a 10MP digital camera has 4x the resolution of a 5MP camera (twice as many pixels in each direction).

In this particular example, 1141 horizontal pixels have to be mathematically combined into 479 pixels, and the number of vertical pixels have to be rfeduced by the same proportion. And since these two values do not have a simple integer relationship, the math to do the pixel combining is not simple because it involves a lot of fractional pixels. In this particular case, the only integer factors of 1141 are 7 and 163, and you would get the best resampling results if you restricted your resizing to an exact multiple of 163 (i.e. 489 to stay close to your desired size.

When you change the dpi setting in FrameMaker, on the other hand, you are *not* changing the resolution of the image because all the pixels are being retained. You're simply telling FrameMaker to reproduce them more closely together.

-Fred Ridder

> From: salt -dot- morton -at- gmail -dot- com
> Date: Tue, 8 Feb 2011 12:22:11 -0800
> Subject: Re: Graphics Resolution Confusion Once Again
> To: techwr-l -at- lists -dot- techwr-l -dot- com
>
> Therein lies your problem. For work that is destined to be printed, try
> using the TIF file format instead.
>
> > Chris
>
> On Tue, Feb 8, 2011 at 12:18 PM, Nancy Allison <maker -at- verizon -dot- net> wrote:
>
> > Oh, yeah -- sorry! It is a .bmp file.
> >
> >
> > Feb 8, 2011 03:10:31 PM, salt -dot- morton -at- gmail -dot- com wrote:
> >
> > What file format are using? That is, what is the file extension of the
> > graphic file?

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Follow-Ups:

References:
Re: Re: Graphics Resolution Confusion Once Again: From: Nancy Allison
Re: Graphics Resolution Confusion Once Again: From: Chris Morton

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