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
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
Thanks to sebsauvage for this tip.
- Try to find the right balance between resolution, image quality and file size in order to avoid major degradation of the image.