imagemagick has been called something like "the swiss army knife of image manipulation utilities." I've utilized this application on many occasions over my years as a GNU/Linux user and been amazed to have as yet found nothing that it cannot do. Moreover, it's a CLI-friendly tool, which makes it doubly appealing for someone like me who favors using the least resource-intensive application for any given job.
I should mention that, not only was I converting these images to a different format with which my laptop could better deal, desirable, but resizing them was needed as well. You see, each photo taken by this fairly high-end camera came in at about 25 megabytes, and the dimensions of each image were probably in thousands of pixels. So I wanted to both resize and convert them; but, based on past experience with imagemagick, I was sure it would be up to the job.
I was surprised, after some initial searching on how to accomplish this task, at how simple this task would turn out to be. After mounting the Secure Digital card on my laptop, I copied over all the images--which had the .CR2 extension, by the way--to a temporary directory on my laptop.
The incantation I then used, after cd'ing to the temporary directory where the images resided, was mogrify -format jpg -geometry 1024x768 *.CR2. It should be fairly obvious what this does, but just in case it's not, let me explain. The mogrify command is part of imagemagick's image manipulating routines and can be invoked to do a number of things with an image, but in this case the -format switch, followed by the jpg extension, tells it to convert from one format to another.
Though most readers of this blog are likely to know this already, it will be worth mentioning that the asterisk preceding the file extension is the wildcard symbol. Thus, all files in that directory with the designated extension get converted. Incidentally, they are given the same prefix as the raw .CR2 files, but after conversion have the .jpg extension instead of the .CR2 extension.
I should mention here that, although raw formats are not especially new, I did run across some indications while researching how to do this, that older versions of imagemagick might not be able to operate on such formats. But I believe any version that's come out in the last 2 or 3 years should understand and be able to manipulate these raw formats.
The -geometry switch tells imagemagick to resize the image from something in the thousands of pixels down to a size that displays better, and takes up a whole lot less disk space, on this laptop. The switch does also have a somewhat undesirable effect on photos taken in vertical rather than horizontal orientation, since, as written to disk, these are taller than they are wide (whereas photos taken in horizontal orientation are wider than they are tall): the program thus makes the height of the photo 768 pixels, while the width, being kept proportional, turns out to be quite a bit less than that. But for my purposes--which was simply being able to view quickly these fresh photos on my laptop--these somewhat under-sized photos did not pose any particular problem.
The process of converting many photos this way can be lengthy, but, as you have seen, it is quite simple. I would simply start the process, then either do some other task in another desktop while awaiting completion, or just set the laptop aside while it was running the process. After about a half hour or so, I was ready to view photos.