03 Dream Weaver


03 Dream Weaver

This is a real world example. This Dream Weaver IX PDF file posted here - www.rcgroups.com/forums/showpost.php?p=2017... - by Algy2 on Dec 19 2011 is our starting point. It is 1,809KB in filesize. The plan will need scaling to full size.


We want to take this PDF and make from it a new PDF document that has 2 pages: 1st page a (full size) plan that is clear and accurate, and prints out at full size. 2nd page the article text. We don't care too much about the size or print quality of this page, so long as text is readable. We want the total filesize of the final PDF document to be under 800KB.


In this tutorial I am using Photoshop CS3.

1. Start by opening the pdf up in Acrobat Reader X and having a look around. The pdf is in 2 pages. When you hover the mouse at the bottom LH corner of the screen, it displays the size of the pages, in inches. Here you can see page 1 is 6.24" x 9.03". Page 2 is the same size, but just turned into landscape orientation. Reading the actual text, notice that bottom of page1 says "Full size copes of the 1/5th scale drawing opposite..." so we know the scaling factor to apply to the plan. Probably. Finally, note on the plan drawing the legend (top left) says the span of the model is 56".


2. Ok. Let's go to work. Drag the PDF into Photoshop, and you get an ImportPDF dialog box. Select the first page, at 200dpi, Greyscale, 8bit:


3. Select all of the page apart from the photo. Do Image/Adjustment/BrightnessContrast to make the text strong and dark:


4. Do Select/Invert, so now just the photo is selected:


5. Do Image/Filter/Pixellate/ColorHalftone, and set the MaxRadius to 4:


6. Zoom out. Select All. Do Image/Adjustments/Posterize to 2 levels. This forces every pixel to either black or white, and eliminates all greys in between:


7. Do Image/Mode/Bitmap to 50% Threshold, still at 200dpi.


8. Do File/SaveAs/Format=PhotoshopPDF. Use the same settings as we did in steps 18-20 of Tutorial 02 and save as 'mypage1.pdf':

Now check the filesize. Mine came out at 135KB. It's here mypage1.pdf if you want to have a look.


9. Ok, lets have a go at the actual plan drawing now. Drag the PDF again into Photoshop, and in the ImportPDF dialog box, select the second page, at 1500dpi, Greyscale, 8bit. Why 1500dpi? You got it. Because 1500 x 1/5 = 300. We always aim at 300 dpi output, and in step 1 we decided this drawing had to be enlarged 500%. Since we are going to be blow this image up 5 times, might as well grab all the detail that's in there. Of course, most likely it was scanned at 600dpi, and that's fine, and we'll mainly be grabbing noise rather than signal, but at least we tried.


10. Zoom out. Do Image/ImageSize. Note page width is 9.52".


11. Untick Resample. Unticking Resample makes the dialogue box options get a lot simpler, with half of it greyed out. Set Resolution to 300dpi, and note how page width immediately updates to 47.6". Apply that.


12. Lets check the scaling is now correct. Drag a guide to the wingtip, and another to the centreline. Select an (any) area that snaps-to between those two guides. Check in the info window what that measured width is. Ok, so that's showing 27.8" which sounds right for a 56" wingspan.


13. Ok. Let's crop the plan edges just to tidy up, and then the rest of the processing for this drawing is all exactly as in steps 14-20 of Tutorial 02 so just to quickly recap: Do Image/Adjustments/BrightnessContrast, Posterize to 2 levels, Bitmap at 50% threshold, Save as PDF. Let's call it 'mypage2.pdf

Now check the filesize. Mine came out at 376KB. It's here mypage2.pdf if you want to have a look.


So. We have 2 processed pdf files now, we just need to merge them.


14. We combine the 2 pages using Pdfsam - http://www.pdfsam.org/ - a free open source tool to split and merge pdfs. Open Pdfsam, and navigate to the folder with your 2 new pdf files.


15. Drag and drop your 2 pages into Pdfsam. Set a name for destination output file. Lets call it 'DreamWeaver.pdf'. Then click Run.


16. Pdfsam merges the 2 files together and saves it as 1 file. Check the final size. Mine came out at 412KB.


That's about it. The finished file came out at 412KB. My copy is here DreamWeaver.pdf if you want to have a look.








The article page we converted to 200dpi (since we don't care so much about print quality with this page) and we kept it at the original print size of ~ 9"x6". We converted the photo on that page into a halftone pattern, to save on filesize.

The plan drawing page we resized to 500%.

Next we scaled up the plan itself, then we combine the 2 pages using Pdfsam.




Hope that all made sense. You can email feedback to: steveWMD@outerzone.co.uk