Daniel said:
Some of the jpegs I have downloaded from newsgroups are HUGE. They are
MUCH larger than they need to be. I have some that are a big as five
MB.
Is there a freeware program that I can tell how large I want it to make
the file and it will make it that size with the best possible quality?
For example if I have a five meg jpeg, I want to tell the program to
reduce the size to 200 KB and have it do it while keeping the visual
quality as high as possible.
Thank you in advance for all replies.
JPEG is a lossy format and the more you recompress the more artifacting
is introduced. Unless the original was compressed at the highest
possible quality setting (unnaturally inflating what should have been
smaller), you're unlikely to achieve a better result without sacrificing
image quality.
Using an app like Gimp (
www.gimp.org) that has extra options for exactly
how you compress the JPEG will allow you better control over the final
result. For example, you have the option of setting the subsampling to
1x1 and using an optimized baseline or not, as well as being able to
input quality parameters interactively and preview the final output and
size. You'll be amazed how dropping from 95 to 93.5 can make a dramatic
savings in size.
Alternatively, filtering out artifacts in Photoshop or automated tools
and then recompressing can sometimes be of use. Generally the JPEG DCT
works best with areas of gradients and low contrast, so smoothing out
sharp areas and edges can help compressibility.
As a side note, depending on the content, it may not be desirable to
recompress any. Such as a very high resolution NASA full field image
(with lots of small details in a large resolution image), or with a JPEG
out of a 8 megapixel camera. In that case it would be better to keep
the source as untoched as possible until you're ready to post-process
the image in Photoshop or Gimp and the like with resizing, color, crop, etc.
