Optimisation and Saving
Optimisation allows to reduce PDF files size. Specific parameters of saved file depend on later usage of the file and properties required for the resulting document.
Please note that optimising file with some compression methods may damage images, which will lead to poor printing quality.
To optimise and save PDF file choose File > Save Optimized As… in main menu or use Ctrl+Alt+S shortcut.
This will open a window, which allows to set following preferences for color and black and white images.
Set following preferences if required.
- DPI — Reduce image resolution to decrease file size.
Resolution cannot be further reduced for images with 16×16 DPI.
- Compression — Decreasing file size with different algorithms. JPEG compression yields best results for photos with smooth color gradients. ZIP is best choice for drawins and patterns with big areas of same color. JBIG2 is applied for black and white pages. If right algorithm is chosen, compression is conducted without losses, and lower quality images are better compressed. Images with text can be better compressed than with CCITT Group 4 algorithm, but compression takes more time. Currently Master PDF Editor uses lossless compression. CCITT Group 4 is also applied for pages with black and white images and is the fastest lossless compression algorithm.
- Quality – Available only for JPEG format. JPEG compression is always done with loss of image quality, since some pixel data are removed without possibility of restoring during compression. Color images are better compressed with lossy JPEG compression algorigm. Quality level around 75-95 has best size-quality ratio. Quality 60-70 yields small picture with acceptable quality. 30-50 quality percentage is optimal when small file size is important and image quality is not prioritised.
Grayscale images are compressed with CCITT, JBIG2 and ZIP without losses.