A good friend from work, Dudulho, gave me this tip. I just refined it a little to improve the result. My problem was that I had 20 images scanned from a workbook and wanted to create a final PDF document combining them all.
Each image was about 1.5 MB on average, which would have produced an impractical file of approximately 30 MB. So I had to do something to reduce the image sizes.
The program I used was IrfanView version 4.1.0. I followed these steps to automate the process:
Menu File -> Batch Conversion/Rename -> Check “Use advanced Options” and click the “Advanced” button. In the new window, just enter the settings shown below:
As you can see in the steps above, I set the maximum height limit to the height of A4 paper (210–297 mm), so I entered 29.7 cm.
I checked the option to preserve proportions, then lowered the dpi from 600 to 150. Finally, I checked the contrast option under other settings and set it to 60. This makes the page more legible by lightening the background while keeping the letters dark.
After setting everything up, I went back to the previous window, added the files I wanted to modify (in this case, all 20 files), and clicked “Start Batch.” Then all I had to do was wait. You can see the final result in the file below:
To combine all the JPG files, I used the “convert image to pdf” software, which is so simple that it needs no explanation. I got a PDF with a final size of 2.3 MB instead of the roughly 30 MB it might have been. A very good result in both size and quality.
If anyone has another image-optimization tip, feel free to leave a comment.
See you later.