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View Full Version : Fixed Cropping of very large images doesn't work



j7n
04.07.2007, 02:26 AM
I tried to crop 433 MB (half gigabyte) image via the custom selection command. Selection was created but when I executed the crop command nothing happened: Irfan was busy about a second and that's all. My guess is that it could not allocate memory but it DID NOT SAY anything.

In fact there was enough memory for about 3 such images. After the unsuccessful crop, my system information tool showed that Irfan had allocated 892,664 kB – twice as needed for display. Is not correct that in theory cropping could require at most twice the memory needed to display the image? You just copy pixels from one location to another and after the process is complete you discard the source data.

j7n
07.07.2007, 01:11 AM
I've found a way to crop images this large. You can use Jasc Paint Shop Pro's "Canvas Size" command with precalculated crop positions (monochrome selection also requires memory). It's better to crop bottom pixels away first and then reload the already smaller image.

Perhaps this thread should be moved to off-topic.

Sjef
07.07.2007, 08:31 AM
I'm very intrested in the kind of graphic file you tried to crop. Was it a Jpeg file? If so is it compressed or not?

j7n
08.07.2007, 12:20 AM
It was an uncompressed section of Google Maps. It might take less memory to cut a JPEG stream, but I don't know any tool that didn't also load the decoded picture into memory.

Sjef
08.07.2007, 05:05 PM
I think it is a IV shortage. I encountered the same problem with a large HiRes Jpeg-scan (6000 x 9000 pixels, 28 MB). IrfanView freezed. I think it was in IV-version 3.25. Now -in version 4- I have no trouble at all with the same file. I suppose your last post gifs the answer: many other tools have no trouble with your large image. Now I've tried to dubbel the size of my large image. The procedure took too much of my patience...

Bhikkhu Pesala
08.07.2007, 06:01 PM
Working fine here on 12400 x 12400 Pixels (153.76 MPixels) image, cropping to 3200 x 3200 pixels. Undo also working. Image was 439.91 MB (461,280,040 Bytes) in memory (not saved), just doubled from my largest Hubble Space telescope image. It takes a while, of course, but not so long that you have to go and make coffee Seconds rather than minutes. My PC is not super powerful, only AMD64 3500 939PIN 1024mb DDR

Sjef
09.07.2007, 08:27 AM
...so it's not a IV shortage at all! Glad to know that, thanks. Now I'm pretty sure it's the small memory of my system (512 MB sdram). It's kind of thrifty, but soon, when I have to get a new (Vista)-system I rather put the money in new memory. Yet the use of my virtual memory (1761 MB on another partition) should fill up the gap I may assume. Other programs (like for instance Photoshop) never cause any memory-trouble.

j7n
09.07.2007, 11:24 AM
Sorry for the trouble, it's working in the most recent version of IV. After the operation is completed IV uses the memory of the original image plus the amount it takes to store the original one. I guess I should have tried to disable Undo, but I had forgotten that it's possible.

I have not used Photoshop, but I believe it treates graphics in blocks that it loads from hard disk. People somehow managed to create pre-press files back then when a megabyte of memory cost $2. So it should be possible. However, I don't think that every user should pirate Ps for some simple operations.