You can export the file to a lossy file format such as JPG ( https://en.wikipedia.org/wiki/JPEG). GIMP has an option to "Show preview in image window", which will also give you an estimate of the file size from the parameters. You can modify the "Quality" slider until you reach a desired file size. Does this help with what you wanted to achieve?

On Thu, Jul 9, 2015 at 2:22 PM rhimbo wrote:

Hi,

I would like to reduce the file size of an image. But I would like to retain
the width/height dimension. Basically, I frequently need to do this to post
images of screen grabs to forums when I have a question and want to show the
important elements.

I've found the Tools -> Transform Tools -> Scale.

I've searched for scale related posts but don't see how to reduce the file size
without affecting the width/height of my image.

Many thanks,

-- rhimbo (via www.gimpusers.com/forums) _______________________________________________ gimp-user-list mailing list
List address: gimp-user-list@gnome.org List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list List archives: https://mail.gnome.org/archives/gimp-user-list

With jpeg, you can change the amount of compression, and you are likely to be fine with the image quality.

You can also change the resolution - the pixels per inch. 72 is typical for the internet; 200 for printing, higher quality for historical quality images. Some display/ formats will also change their physical size.

I'm not sure if gif offers compression or not.

Dora

-----Original Message----- From: Pat David
Sent: Thursday, July 09, 2015 5:40 PM To: rhimbo ; gimp-user-list@gnome.org Cc: notifications@gimpusers.com
Subject: Re: [Gimp-user] How to reduce image file size while retaining width/height of image?

You can export the file to a lossy file format such as JPG ( https://en.wikipedia.org/wiki/JPEG). GIMP has an option to "Show preview in image window", which will also give you an estimate of the file size from the parameters. You can modify the "Quality" slider until you reach a desired file size. Does this help with what you wanted to achieve?

On Thu, Jul 9, 2015 at 2:22 PM rhimbo wrote:

Hi,

I would like to reduce the file size of an image. But I would like to retain
the width/height dimension. Basically, I frequently need to do this to post
images of screen grabs to forums when I have a question and want to show the
important elements.

I've found the Tools -> Transform Tools -> Scale.

I've searched for scale related posts but don't see how to reduce the file size
without affecting the width/height of my image.

Many thanks,

-- rhimbo (via www.gimpusers.com/forums) _______________________________________________ gimp-user-list mailing list
List address: gimp-user-list@gnome.org List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list List archives: https://mail.gnome.org/archives/gimp-user-list

rhimbo writes:

I would like to reduce the file size of an image. But I would like to retain the width/height dimension. Basically, I frequently need to do this to post images of screen grabs to forums when I have a question and want to show the important elements.

I've found the Tools -> Transform Tools -> Scale.

For what you're doing, it's usually easier to use Image->Scale Image... rather than the Scale tool. By default, if you change Width, the Height will change automatically, keeping the aspect ratio (that's the term for that width/height ratio) the same.

The Scale tool is for when you need to adjust the size of a layer interactively, maybe to match something else in the image; you don't know beforehand how big you want the layer to end up. If you prefer using that to Image->Scale Image..., you can set it to keep the aspect ratio the same by checking "Keep Aspect" in the tool options dialog, or by holding the Ctrl key down as you drag.

Scale Image: http://docs.gimp.org/2.8/en/gimp-image-scale.html Scale Tool: http://docs.gimp.org/2.8/en/gimp-tool-scale.html

...Akkana

On 07/09/2015 08:55 PM, Dora Smith wrote:

I'm not sure if gif offers compression or not.

Depending on the image content, GIF files may be noticeably larger or smaller than equivalent JPG files. PNG files will usually be substantially larger than either.

The GIF format is an indexed format: Every color in the image is assigned a numerical value, and the individual pixels are referenced to the resulting table. In some instances, a GIF file will be smaller than an equivalent JPG file, especially where the number of unique colors in an image is low, i.e. line art, cartoons, logos etc. Photographic content, not so much.

Why nobody uses GIF any more:

GIF does a very poor job of rendering gradients, i.e. photos with lots of clear sky or smooth shiny objects, due to its limited storage space for the values of unique colors: Smooth transitions in an image are rendered as a series of bands with visible edges when converted to GIF. Even where this is not a problem, GIF renderings of photographic content are usually larger than equivalent JPG files.

The result of scaling a GIF file to a larger or smaller size, or editing color values in one, is horrible. The first step when working on a "found" GIF file in the GIMP is to do Image > Mode > RGB. If the edited file will be exports as a GIF, the GIMP will convert the image back to indexed format during the export process.

At one time GIF was the only browser compatible format with transparency, but since it only has one value for transparency (100%) it has major aliasing problems - transparent regions that are not rectangular have jagged or stair-step edges when viewed against a contrasting background. PNG has a real alpha channel, enabling partial transparency which anti-aliases transparent regions very nicely, so these days that's what people use when transparency is required for web graphics, or to make image content with transparency portable across all common image editing tools.

Another GIF feature, much overlooked today, is animation: Multi layer image files can be saved as GIF animations, and the GIMP has a tool for optimizing animated GIF file size by removing content that does not change from frame to frame in the individual layers.

Internet advertisers abandoned animated GIF banners when Flash evolved into a user tracking spyware tool, and there are not many use cases for GIF animation in web design these days - Flash and Javascript can do more of the stuff web designers like. I have not made a GIF file for a decade or so.

:o)

On 11/07/15 00:17, Steve Kinney wrote:

Depending on the image content, GIF files may be noticeably larger or smaller than equivalent JPG files. PNG files will usually be substantially larger than either.

For screenshots(*) and lost CGI, PNG is usually significantly smaller than either GIF or JPEG. And you cannot reduce the quality too much on JPEGs for images with hard edges such as screenshots.

(*) unless of course the screenshot contains a photo...

Ofnuts writes:

On 11/07/15 00:17, Steve Kinney wrote:

Depending on the image content, GIF files may be noticeably larger or smaller than equivalent JPG files. PNG files will usually be substantially larger than either.

For screenshots(*) and lost CGI, PNG is usually significantly smaller than either GIF or JPEG. And you cannot reduce the quality too much on JPEGs for images with hard edges such as screenshots.

(*) unless of course the screenshot contains a photo...

I recommend everyone test this out for themselves. I find my screenshots are usually much larger in PNG, but it depends on what sorts of windows you shoot. In my case it's usually browser or GIMP windows.

Of course, if you need to edit the screenshot before passing it on (e.g. adding arrows or annotations) then PNG is better since it's non-lossy.

...Akkana