On 12/10/16 10:08, Deixis wrote:

Does anyone know any tricks on how to resize extremely large images? I can't even open this computer generated .PNG. It's about 1 GB in size and I tried various tools so far to resize it. None of them can even open it. There must be some trick I can use?

Trick=Bigger computer with 64-bit CPU/architecture, OS and applications :)

Otherwise if you don't tell us the tools tested already people will likely suggest those you have already tried.

Me, I would try ImageMagicks' 'convert' utility.

On Wed, 2016-10-12 at 10:08 +0200, Deixis wrote:

Does anyone know any tricks on how to resize extremely large images? I can't
even open this computer generated .PNG.

I'm going to guess you are using a Linux system in this answer. Life is too short for me to try telepathy.

If you run the file command on the image file in a terminal, file foo.png
or
identify foo.png
do you get a size in pixels?

I routinely open 10,000 x 20,000 pixel images in gimp.

A good rule of thumb is the amount of memory you need will be width * height * 4 (assuming an 8-bit colour image) in bytes, e.g. for a 100,000 x 37,000 pixel image it's 100000 * 37000 * 4
which gives 14800000000 bytes
dividing by 1024 * 1024 (megabytes) gets 14114 megabytes
and dividing that by 1024 gives
13.7 gigabytes.

So to open this (fictional) image you'd want probably 16G of RAM or more in your 64-bit computer. On a 32-bit computer you'd want at least 20GBytes of swap.

The size of the image file on disk just reflects how well or badly the PNG compression has worked, but if it's worked well, the image could easily need over 100G of memory, which you could do by adding a large amount of swap space and being very patient.

Without more information about the image and your setup it's hard to guess and give more advice on which tools would be best.

Liam

Does anyone know any tricks on how to resize extremely large images? I can't even open this computer generated .PNG. It's about 1 GB in size and I tried various tools so far to resize it. None of them can even open it. There must be some trick I can use?

Hate this mailing list format

However scaling down a very large image can be done using an application nip2.

see: http://www.vips.ecs.soton.ac.uk/index.php?title=VIPS

I have not tried this in Windows, I use linux. Windows versions can be found at http://www.vips.ecs.soton.ac.uk/supported/current/win32/ Despite the "/win32" the zips are named "_w64", so I assume 64 bit. no installer, unpacks to folders.

For this demo (in linux) scaling a 1197 MB png to a 20 MB jpg.

https://youtu.be/76Xn5BIrl2Y 4 minutes

I can't seem to spot nip2 in the directory structure. Vips itself also seems to be a dos/command prompt application, I don't get an interface when running the vips executable.

Many appologies, I gave bad info on the nip2 for windows download. Not Nip2

You have to go back a couple of sub-versions to get a windows installer.

http://www.vips.ecs.soton.ac.uk/supported/8.2/win32/nip2-8.2b-setup.zip

This in a Win10 Virtual machine (with limited resorces) just to see how it installs.

Installs to a strange location but let it go there. You will find it in the Win10 applications. See the screenshot

Thank you. Yes, the program works but if I load the png in it, it instantly crashes with a typical Windows error that doesn't tell me anything. If I run the program again it asks me if I want to delete 319.50 MB of temp files from the temp area. Clearly it is doing something.

It might be worth having another go. As before I use mainly linux, keep a Windows virtual machine to see the problems Win users experience with Gimp.

This Win 10 VM is short on resources, 2 GB memory and not much free disk space. Amazed that it works.

15 minutes to load the 1,225,877 KB png, 18 minutes to render a 10% scaled png 32,561 KB

see the screenshot and check the bottom left corner. I started with 2.02 GB free and ended with 1.11

Personally, I do not think that ImageMagick will scale that down. I get error messages here, but the place to ask is the IM forum where they are very helpful.

http://www.imagemagick.org/discourse-server/ users section.

Be it on your own head, but if had no further use for them, I would go ahead and delete the 319.50 MB of temp files from the temp area. Just make sure they're not currently doing something important. You might empty your Recycle Bin, too. It gives your machine headroom.

I reiterate, the responsibility is yours.

RS

-----Original Message----- From: Deixis
Sent: Thursday, October 13, 2016 8:57 AM To: gimp-user-list@gnome.org
Cc: notifications@gimpusers.com
Subject: [Gimp-user] Can't open extremely large .PNG

Many appologies, I gave bad info on the nip2 for windows download. Not Nip2

You have to go back a couple of sub-versions to get a windows installer.

http://www.vips.ecs.soton.ac.uk/supported/8.2/win32/nip2-8.2b-setup.zip

This in a Win10 Virtual machine (with limited resorces) just to see how it installs.

Installs to a strange location but let it go there. You will find it in the Win10 applications. See the screenshot

Thank you. Yes, the program works but if I load the png in it, it instantly crashes with a typical Windows error that doesn't tell me anything. If I run the
program again it asks me if I want to delete 319.50 MB of temp files from the
temp area. Clearly it is doing something.

Deixis (via www.gimpusers.com/forums)

On Thu, 2016-10-13 at 01:42 +0200, Deixis wrote:

 

Oh my gosh I'm sorry, I forgot that Gimp is released on more than just Windows.

It's OK, but giving information about your system is really really important when asking for help with software crashes.

Yeah, I run in on Windows 10. I do have exactly 16 GB of ram, but only about 40 GB of free disc space left.

Windows might need a large swap file (on the same partition as the main Windows disk, good old C: itself) so that might be a problem. Also make sure you have downloaded 64-bit versions of GIMP or whatever you're using.

Is there perhaps just a way to cut the image into muliple images?

Most software to do that will need to load the image into memory.

Do you know the dimensions (size in pixels) of the image? And whether it's RGB colour or greyscale?? Or is the image publicly available somewhere? And, what size do you want to end up with?

Does Windows Picture Viewer open the image? IrfanView is popular but has a 32-bit limit on file size, so even though your PNG image is only one gigabyte in disk size, it's compressed; if it uncompresses to more than 4 gigabytes, IrfanView will probably crash, as will most other 32- bit programs.

Some other programs: * http://www.fastpictureviewer.com/ [view only, no resize] * http://delhoume.frederic.free.fr/vliv.htm can export the current zoom view; shareware
* http://fwtools.maptools.org/ (may be hard to use)

Liam

I meant *image*, not map. Sorry. Yeah the image is a map. A Minecraft map, specifically of an unusually large world. I didn't want to say that, but I don't really want my wording to be misunderstood at this point.

Looking at your posts on IM-users, you have plenty of resources, maybe not enough disk space, so why not move that big file out to usb storage and accept some long processing times.

Apart from that, I think some of the problem is self-inflicted. Changing IM folder name etc...not a good idea.

While I still do not think IM will work for a 1GB png image, since it is installed you can get some information which might assist others to help.

Look at the attached screenshot:

Open the (lame) Win10 file manager in the folder containing the large png.

1. Up at the top in the location, type cmd then enter. This will open a terminal in that folder.

2. At the prompt \> type path (enter) and check that IM is in the correct place. (otherwise uninstall/re-install)

3. type in the command using your image name magick identify myimage.png

Does it show something like the screenshot? Is it really a png? Is it broken?

Post the information and hope someone will assist. I do know that nip2 will work with very limited resources in Win10, but you have to be patient.

So your image is 90 feet square at 300 dpi? That is a rather large image for anybody's computer.

RS

-----Original Message----- From: Deixis
Sent: Saturday, October 15, 2016 6:49 AM To: gimp-user-list@gnome.org
Cc: notifications@gimpusers.com
Subject: [Gimp-user] Can't open extremely large .PNG

3. type in the command using your image name magick identify myimage.png

Does it show something like the screenshot? Is it really a png? Is it broken?

Post the information and hope someone will assist. I do know that nip2 will work with very limited resources in Win10, but you have to be patient.

It says:

C:\Program Files\ImageMagick-7.0.3-Q16>magick identify 1.png 1.png PNG 327168x325632 327168x325632+0+0 8-bit sRGB 1.0255GB 0.000u 0:00.000

Well, that's rediculously large. At least it's definitely a png.

Deixis (via www.gimpusers.com/forums)

On 10/15/2016 10:26 AM, Deixis wrote:

C:\Program Files\ImageMagick-7.0.3-Q16>magick identify 1.png 1.png PNG 327168x325632 327168x325632+0+0 8-bit sRGB 1.0255GB 0.000u 0:00.000

Well, that's ridiculously large. At least it's definitely a png.

You could try Nconvert. It is designed specifically to convert one image format to another, and has a *lot* of options.

James Moe
moe dot james at sohnen-moe dot com
520.743.3936
Think.

On Sat, 2016-10-15 at 12:49 +0200, Deixis wrote:

 

C:\Program Files\ImageMagick-7.0.3-Q16>magick identify 1.png 1.png PNG 327168x325632 327168x325632+0+0 8-bit sRGB 1.0255GB 0.000u 0:00.000

OK, so this will need approx. 400 gigabytes of swap space, maybe as much as twice that.

If you want to try working with it, you should get a spare 1T or 2T hard drive.

In the netbpm tools the pamscale program reads a single raster row at a time, so it can probably handle your image. You'd need to use something like (in the command line, netpbm does not have a GUI)

pngtopnm -byrow thefile.png | pamscale -reduce 1024 -linear | pnmtopng

smallfile.png

https://sourceforge.net/projects/netpbm/ (make sure you get a 64-bit version though)

But it would be better to regenerate the image!

Liam