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Image Manipulation to shrink JPEG file size.

Hi,

I have an image, the dimensions must stay the same i.e. X x Y pixels.

Now I know when saving a JPEG I can lower the quality option which will result in a smaller file size.

Is there anything else I can do to reduce the file size while maintaining the same physical size?

Cheers,

Dale
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Dale Burrell
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Dale Burrell
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1 Solution
 
enachemcCommented:
make it black and white
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enachemcCommented:
decrease the number of colors used (bits per color)
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Dale BurrellDirectorAuthor Commented:
OK, I want to keep it in colour, what would I do in photoshop for example to reduce the colours?
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enachemcCommented:
use irfanview (free)
Image -> decrease color depth
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sylenixCommented:
i'm using Yahoo! Smush.it for my image compression needs. i find it very easy to compress my files & you could even see the percentage that you saved after the compression. the site is super easy to use and it uses a superb optimization technique to remove unnecessary bytes from your images and it even zip your file after compression so you can download it back fast.
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aleghartCommented:
File > Save for web and devices

Decrease quality.
Increase blur.

In that order.

The more you decrease quality, the more artifacts you get.
When you're very close to your target size, you can increase blur...you lose detail, get some smoother transitions, and shave that last little bit from the file size.

You can decrease color depth in other formats like TIFF and GIF.

 aleghart-427824.flv
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Dale BurrellDirectorAuthor Commented:
Awesome aleghart! That really helps... now I should give you the full story, I posted this question to help me understand my options, but I am actually intending to implement this functionality in software, specifically in http://www.neodynamic.com/Products/IDWebC/ImageDrawWebControl.aspx?tabid=24&prodid=4

I have full control over the JPEG quality, and I can control the blur, but I am wondering if blur is something that should only be played with when one can see the result? If I automatically apply a blur in software it may not always look good great?

It sounds like the JPEG quality is certainly the main consideration, and that colour depth etc is not applicable in this case?

How does one find out what actually happens with a 'save to web' anyway?
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aleghartCommented:
"save to web" is just to indicate the purpose of the module.  It is designed for small files, and allows a preview 2-up or 4-up of different resolutions so the operator can view the results of different settings.  The final file is saved on a hard drive just like a "Save As..." command.

Once a file is saved with destructive compression, it should not be edited again...the original should be used to generate a new web version.  JPEG is destructive.  GIF even moreso as you alter color depth.

The results are difficult to predict, as every image has different details.  What works for a 1-color logo will not be the same as a full-color headshot or Ansel Adams landscape.  That's the strength of that module...seeing what you're going to get.

Of course that all goes out the window when the file is viewed on a different monitor with different resolution, color calibration, gamut, temperature, and ambient conditions.  :)
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Dale BurrellDirectorAuthor Commented:
Cheers
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