Extract image from GIF using index

howa · Post by **howa** » 2006-09-18T07:10:34-07:00

to extract image from animated gif, using index

such as. convert test.gif[0] test2.gif

but if the input is not animated gif, such as jpg, png, will there be any harmful effect?

e.g.

convert test.jpg[0] test2.jpg

from my testing, seems they are ok, isn't?

Post by **magick** » 2006-09-18T07:42:15-07:00

There are no side-effects when appending [0] to a non-animated image format such as imaage.jpg[0].

howa · Post by **howa** » 2006-09-18T07:47:24-07:00

thanks first...

one more question...

which parameter can set the quality for all input file types, such as gif, png, and jpeg?

seems `quality` only apply to png & jpeg

i want a global command which can set the quality and hence control hthe file size no matter the input type

thanks.

Post by **anthony** » 2006-09-18T16:52:39-07:00

GIF does not have a quality, though it does have a compression. Most people just leave this as default though.

GIF is limited to a maximum of 256 colors, minus one is transparency is wanted.
JPEG is lossy and losses information, such that it is a minimal loss visually for real world images. PNG quality is NOT a percentage as it is for JPEG, and does not loss information, but is also a lot larger to store images.

See IM examples, Common Formats for a summary and more details.
http://www.cit.gu.edu.au/~anthony/graph ... s/#summary

glennrp · Post by **glennrp** » 2006-09-22T14:40:34-07:00

identify -verbose file.gif

Post by **anthony** » 2006-09-22T23:25:38-07:00

For a more concis figure...

Code: Select all

identify -format %n image.gif

What do you need it for? Generally you try to create commands that do not depend on the number of images in a animation, though that is not always posible.

Post by **anthony** » 2006-09-23T19:02:00-07:00

To divide up all the frames use +adjoin to turn off 'merge multiple images into one file'.
See examples and file numbering in
IM Examples, Image File Handling, Writing a Multi-Image Sequence
http://www.cit.gu.edu.au/~anthony/graph ... #write_seq

You may also like to look at the special scripts in Animation Basics Page.
Specifically "gif2anim" and "anim2gif"
http://www.cit.gu.edu.au/~anthony/graph ... /#sequence

This script not only seperates out the individual frames of the animation, but also generates a ".anim" file that lists the IM "convert" options needed to re-produce the original animation.
That is all the time delays and GIF frame disposal methods that were used for each frame in the animation.
Quite a number of options too.

The "anim2gif' script reverses the process by substitung the BASENAME and feeding the file to "convert".