* ChadDavis [02-22-08 17:21]:

I'm trying to take some screen captures that will be used in a book. How do I set the resolution / dpi of the screen capture device? I tried setting the defulat new image parameters, but it doesn't seem to be used by the screen capture device.

not worth the bother as screen resolutions are 75-100 dpi. You get that which it is.

You can use Image->scale image to directly set the DPI. In X11 it's possibly to directly set the dpi of the screen; however if you did that, printing would probably be huge (as patrick says, typical display devices are 75..100 DPI)

If it were me, I'd write a script I could use from GIMP to set image DPI to 300,300. the pdb call needed is gimp-image-set-resolution (image, 300, 300)

On Sat, Feb 23, 2008 at 8:47 AM, ChadDavis wrote:

I'm trying to take some screen captures that will be used in a book. How do I set the resolution / dpi of the screen capture device? I tried setting the defulat new image parameters, but it doesn't seem to be used by the screen capture device.

On Friday 22 February 2008, ChadDavis wrote:

I'm trying to take some screen captures that will be used in a book. How do I set the resolution / dpi of the screen capture device? I tried setting the defulat new image parameters, but it doesn't seem to be used by the screen capture device.

When doing screen captures, you don't actually get any ppi at all, you just get the plain pixels. The resolution you attach to the image is quite arbitrary. When using it in a book, you might want to scale the image by an integer scale with next neighbour "interpolation" though. IMHO pixelized screenshots look better than blurred ones on paper. But maybe one of the actual book writers on this list may tell you more. *hint*

Greetings, Daniel

On Fri, 2008-02-22 at 23:41 +0100, Daniel Hornung wrote:

But maybe one of the
actual book writers on this list may tell you more. *hint*

I guess that's my cue. :-)

The screen resolution is in pixels. One pixel = one dot. Most monitors give you between 72 and 100 DPI, or dots per inch. You'll notice that you have a monitor that is 15"-24" inches across depending on how they measure such things. So you have 72*15 = 1080 dots across the screen for the 15" monitor. Now how do you convert that to printing for a book?

Well, in the book you want the same image but at a smaller size. A typical book is likely less than a typical piece of paper (around 8.5"). In fact, the actual image size is likely to be around 2"-4" across. So what DPI do you need to squeeze 1080 dots into (splitting the difference) 3"? 1080/3 = 360DPI. If you set your image resolution (using Image->Scale Image and changing the X and Y resolution) to 300 DPI, then your image will be 3.6" across. How do I know this?

1. Create a new image (blank white background) at any size. 2. Image->Scale Image, then set the width to 1080 pixels. Click on "Scale" to scale the image to that size. 3. Image->Scale Image, then set the resolution to 300 for the X and Y resolution. Click on "Scale" to change the image resolution. 4. Image->Scale Image, then change the options menu next to the "Height" field from pixels to inches. Now you can see how wide your image is going to be when it's 1080 pixels across.

Clear as mud? Try it a few times. It's not that hard to grasp once you see it in action.

On Fri, 2008-02-22 at 16:01 -0700, ChadDavis wrote:

But doesn't this mean that if my the portion of the screen that I'm interested in is only 3 by 5 or so, then there is basically no way to get a non extrapolated set of pixels that will print to 3 by 5 on the page?

That's correct. It's the nature of the hardware. You can change the DPI from 300 to 72 to match the monitor but the print will likely be of much lower quality.

You can scale up the screen shot but I'd only double it's size once to produce a larger print image at high DPI. Even then, you're likely to have a less than ideal print image. Scaling up is not a good thing with raster images.

For what it's worth, I tend to make all my screen shots for books and magazines set to 250DPI, which produces a slightly larger print image at reasonable quality.

I would say that it's widely accepted that if you are including an image in a book that represents a screen shot that is less than full screen, you will magnify the image and use blocky pixel replication for text or line graphics, and interpolated zooms for photographic subjects. I think the readers will understand and be OK with that.

If your topic is vector graphic based, such as PDF or SVG, then it may be reasonable to zoom your area of interest to a nice full screen smooth and sharp image for screen shots, but you have to be careful not to misrepresent what you are doing to the reader.

There is a screen that's close to 300dpi, but it's only about an inch across on my iPod ;-), so I don't expect that to help.

-Ken

ChadDavis wrote:

But doesn't this mean that if my the portion of the screen that I'm interested in is only 3 by 5 or so, then there is basically no way to get a non extrapolated set of pixels that will print to 3 by 5 on the page?

On Fri, Feb 22, 2008 at 3:57 PM, Michael J. Hammel > wrote:

On Fri, 2008-02-22 at 23:41 +0100, Daniel Hornung wrote: > But maybe one of the
> actual book writers on this list may tell you more. *hint*

I guess that's my cue. :-)

The screen resolution is in pixels. One pixel = one dot. Most monitors
give you between 72 and 100 DPI, or dots per inch. You'll notice that you have a monitor that is 15"-24" inches across depending on how they measure such things. So you have 72*15 = 1080 dots across the screen for the 15" monitor. Now how do you convert that to printing for a book?

Well, in the book you want the same image but at a smaller size. A typical book is likely less than a typical piece of paper (around 8.5").
In fact, the actual image size is likely to be around 2"-4" across. So
what DPI do you need to squeeze 1080 dots into (splitting the difference) 3"? 1080/3 = 360DPI. If you set your image resolution (using Image->Scale Image and changing the X and Y resolution) to 300 DPI, then your image will be 3.6" across. How do I know this?

1. Create a new image (blank white background) at any size. 2. Image->Scale Image, then set the width to 1080 pixels. Click on "Scale" to scale the image to that size. 3. Image->Scale Image, then set the resolution to 300 for the X and Y resolution. Click on "Scale" to change the image resolution. 4. Image->Scale Image, then change the options menu next to the "Height"
field from pixels to inches. Now you can see how wide your image is going to be when it's 1080 pixels across.

Clear as mud? Try it a few times. It's not that hard to grasp once you
see it in action.
--
Michael J. Hammel Principal Software Engineer
mjhammel@graphics-muse.org
http://graphics-muse.org ------------------------------------------------------------------------------ He doesn't have ulcers, but he's a carrier. -- From a real employee performance evaluation.

Michael J. Hammel writes:

On Fri, 2008-02-22 at 23:41 +0100, Daniel Hornung wrote:

But maybe one of the
actual book writers on this list may tell you more. *hint*

I guess that's my cue. :-)

Me too :-) except Michael has already covered it so well. The only thing I'll add is that when I first started, I was worried about one of Apress' guidelines that said they wanted a particular dpi, so I started out being careful to set the dpi after taking screenshots. I was also sending high-resolution versions of non-screenshot images.

Once we got rolling, it turned out that their layout people scaled each image to an appropriate size on the page, and nobody really cared what dpi the images claimed to have. As long as I took normal GIMP screenshots of reasonably-sized windows, everybody was happy.

The Apress style guide also had warnings about not using Windows Print Screen, and more warnings about various other programs to avoid under Windows (mostly color depth issues, I believe). None of that was a problem with the GIMP screenshots, which worked fine.

Michael J. Hammel writes:

On Fri, 2008-02-22 at 23:41 +0100, Daniel Hornung wrote:

But maybe one of the
actual book writers on this list may tell you more. *hint*

I guess that's my cue. :-)

Akkana Peck wrote:
Me too :-) except Michael has already covered it so well. The only thing I'll add is that when I first started, I was worried about one of Apress' guidelines that said they wanted a particular dpi, so I started out being careful to set the dpi after taking screenshots. I was also sending high-resolution versions of non-screenshot images.

Once we got rolling, it turned out that their layout people scaled each image to an appropriate size on the page, and nobody really cared what dpi the images claimed to have. As long as I took normal GIMP screenshots of reasonably-sized windows, everybody was happy.

The Apress style guide also had warnings about not using Windows Print Screen, and more warnings about various other programs to avoid under Windows (mostly color depth issues, I believe). None of that was a problem with the GIMP screenshots, which worked fine.

Where can you get a copy of this Apress style guide? I searched their site but was unable to see this guide.

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