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How to lower the size (in bytes) of an image?

April 2015


How to lower the size (in bytes) of an image?



If you find that your JPEG files are too heavy ( sending a mail or to publishing image files a web page), here's how to optimize their size :

Step 1 (optional): Skip GREYCstoration on the image


GREYCstoration can optimize your image files by removing the minor variations in pixel intensities.

Step 2: Lower the resolution


For example, if you take a photo with a 5 Mega-pixel digital camera, the dimensions of the image will be 2592 x 1944 pixels, which is far too big for a web page.
  • Lower the resolution, eg 640x480 or 800x600. This is sufficient for a clear and precise image.
  • Some softwares: XnView and Gimp

.**XnView can perform batch conversation.

Step 3: Lower the quality


You can choose the quality of JPEG files, (between 1% and 100%):
  • 1% is the lowest quality, but also gives smaller files.
  • In most cases, 40% is sufficient.

Step 4: Remove unnecessary information

  • JPEG files can contain many things besides the image itself: a miniature of the image, the parameters of the software use to create the file, the camera settings (focus, exposure ...) .
  • It is possible to delete such information with a program like PureJPEG (free):
  • Run the following command: purejpeg myimage.jpg

Conclusion

  • Try to find the right balance between resolution, image quality and file size in order to avoid major degradation of the image.


Thanks to sebsauvage for this tip.
For unlimited offline reading, you can download this article for free in PDF format:
How-to-lower-the-size-in-bytes-of-an-image.pdf

See also

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Original article published by sebsauvage. Translated by netsa77. - Latest update by jak58
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