Mac OS — decrease pdf size via Preview app

• 08, 07, 2021
•  bullgare
•  MasOsX, Soft and services
• No Comments.

To decrease the size of the .pdf filled with images, in Preview you can go to Export and set Quartz Filter→Reduce File Size before saving.

If the images are too blurry for you, you can add your own profile.
1. Create a directory — /Library/Filters.
2. Add new filter file with unique filter — i.e. Reduce Size with good quality.qfilter.
3. The file should contain XML with new filter — you can base on the /System/Library/Filters/Reduce File Size.qfilter file or use the one below. Change compression setting, image size and add unique display name for your filter.

The problem is - the default filter used during conversion has very low conversion settings.

Thankfully, a custom filter can be added.

Adding custom filter step by step
Create new directory (if you don't have it) - /Library/Filters
Add there new filter file with unique filter - f.e. Reduce Size with good quality.qfilter
The file should contain XML with new filter - you can base on the /System/Library/Filters/Reduce File Size.qfilter file or use my below example. Change compression setting, image size and add unique display name for your filter.
Filter file structure/example
I marked key settings by comments.





    Domains
    
        Applications
        
        Printing
        
    
    FilterData
    
        ColorSettings
        
            DocumentColorSettings
            
                CustomLHSCorrection
                
                    8
                    8
                    8
                
            
            ImageSettings
            
                Compression Quality
    
                0.75
                ImageCompression
                ImageJPEGCompress
                ImageScaleSettings
                
                    ImageScaleFactor
                     
                    0.75
                    ImageScaleInterpolate
                    
                        
                    ImageSizeMax
                    1684
                    ImageSizeMin
                    1200
                
            
        
    
    FilterType
    1
    Name

    Reduce Size Good Quality

Further reading — https://apple.stackexchange.com/a/297418/347848