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JPEG save - percentage parameter for targeting file size or original quality est.

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    Requested JPEG save - percentage parameter for targeting file size or original quality est.

    A useful parameter for two of the JPEG save options would be to specify a percentage of the existing file size or quality.

    Specifically, the existing options that would be affected would be:

    1) Set file size: ___ KB (RIOT PlugIn)
    2) Try to save with original JPG quality (estimation)

    An example of the first feature's usefulness might be the making of a copy of a directory tree of JPEG files that would fit on a certain media, i.e. if the source collection of images was 40GB, reducing it to 23GB would fit on a single layer Blu-Ray disc.

    An example of the second might be a similar situation only in which the exact file size isn't a concern, but wishing to save disk space is while still maintaining acceptable quality.

    Thoughts?

    #2
    This would not work well unless you know that the compression of the images was all the same to start with. A high quality JPG compressed at an IrfanView setting of 90 would be about 50% of one compressed at 100. However, a low quality JPG compressed at a setting of 25 would be unusable if compressed to half the size.

    In my opinion, the best solution if you're trying to save disk space is to decide what is the lowest acceptable compression/quality trade off, and always use that. However, that is also far from ideal, as some images look fine at 25 quality, while others look poor at anything much below 90. (Images with text or sharp contrast, fine lines, etc.)

    The attached image Shutters 90 is about half the size of Shutters 100, and Shutters 12 is less than half the size of Shutters 25. Shutters 13 is 22 Kbytes, not much smaller than Shutters 25, but much worse quality.

    You may also noticed if you check the file information dialogue for each image that the estimated compression is some way off what was actually used at the low end of the scale.
    Attached Files
    Last edited by Bhikkhu Pesala; 06.10.2014, 09:50 AM.
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