Legacy ImageMagick Discussions Archive

anthony wrote:QUESTION: how did a 30000x300000 pixel JPEG image get created in the first place if most programs are insufficient memory?

I've done it with photoshop, quite smooth also. Probably they're more practice with memory managment

This is my conversation with guido from the jpeg group: Hi, sorry for the direct mail. I'm trying to crop (extract) a part of a big image, with the minimum resource usage. I've tried lot of solutions but i haven't found one working. I've started my tests with a 12000x12000 pixels image, http://goes ...

Yeah but that won't be don in parallel way, that's my problem. :/ Hope Guido responds fast.

jpegtran -crop 100x100+123+425 -copy none huge.jpeg crop.jpg convert crop.jpg -gravity SouthEast -crop 100x100+0+0 +repage crop_fixed.png Are the same arguments used for jpegcrop? If so that may be the better suggestion, so as to avoid confusion with the multiple versions of jpegtran. I've linked ...

it still takes too much time. But way less time than with a normal "convert -crop" - on my system, this would take not 10 seconds, but 10 minutes! (As convert really reads the full image, and that's too big for my RAM, so sloow swapping starts.) Well sure, but i think there is a faster way, i think ...

But at least that image works again with my ImageMagick installation - and the stream/convert solution is relatively fast: 10 seconds (with my rather old system). 10 seconds? mmhh,, can you please post the command used? So i try that also, and the version of imagemagick used. EDIT: nm i've tried ...

By the way: huge4.jpg has 2x2 subsampling (block size 16x16), so you would have to use the multiples of 16 - if it would work with that image. :wink: And, I think, it's progressive. Now I don't know the internals of progressive JPGs, but it's possible that the complete file has to be read with that ...

So, these are my tests: Downloaded this , the one you can find in the "Lossless crop 'n' drop (cut & paste)" part of this page . Test #1: Image: Lighthouse image from windows 7 pictures Size: 1024x768 Command: .\jpegtran.exe -crop 100x100+0+0 .\Lighthouse.jpg output.jpg Time took: 76 ms Test #2 ...

Sure, give me some minutes, i need to install windows and then i'll post examples too.

Just a thing, what you mean with final cleanup?

My friend tried for me (i'm on mac), seems working, 1 second to output a desidered portion of an image
But i need more testing

PS: now i think someone shold implement this in imagemagick to add features

Maybe the Lossless crop 'n' drop function? let me try..

My problem is how do you check those 8x8 blocks, they won't have the same size in the raw file and afaik there isn't a library that permit that but i think is theorically possible.

This guy here made a quick explanation of how it works but it would be hard and long to make it that way.

With very large images, "stream" is one possibility. See also here: http://www.imagemagick.org/Usage/files/#massive http://www.imagemagick.org/script/stream.php Example: stream -map rgb -storage-type char -extract 100x100+0+0 image.jpg - | convert -depth 8 -size 100x100 rgb:- output.jpg The command ...

Np, thank you anyway. I hope someone will help for this because i don't want to learn all that huffman related things to read a jpeg from hex

what version of IM are you using? perhaps upgrade? also see http://www.imagemagick.org/Usage/formats/#jpg_read but I don't really use it much so cannot say if there is a bug in your version or not. i'm using version 6.6.7, bytheway probably reading "just enough of the input" doesn't mean reading ...