02 Curtiss Jenny
We want to make a (full size) PDF plan from this (small) JPG. We know the wingspan of the finished model is 36in. We want the PDF to be clear and accurate, to print at full size, and to have as small a filesize as possible.
In this tutorial I am using Photoshop CS3.
1. Start by opening the jpg in Photoshop and having a look around. On the top menu do: Image/ImageSize. This displays the info. The print size is only 4". Also it's only 1200 pixels high. We know the pages of the magazine (Model Airplane News, 1952) were about 8" by 10". So most likely this was scanned at around 72dpi.
2. Ok. Let's go to work. Set the image mode to greyscale:
3. Now rotate the canvas 90° CCW:
4. To line the plan up to the horizontal, we need to know how far away from horizontal it is. Zoom in and use the ruler tool. If you can't find it, it is hidden under the eyedropper. Use the ruler to draw a line between 2 points along the fuselage centreline (or any other datum you like). As you draw the line, notice the options window displays the exact angle of the line, in real time. Here it is showing -1.4°. So that is the exact amount the plan needs rotating:
5. Select: Image/RotateCanvas/Arbitrary, and a dialog box pops up suggesting we use that angle to rotate the canvas. To be exact, it's saying 1.39°. Apply that.
6. Now the plan is nicely lined up, let's crop the untidy edges off:
7. Now the plan needs scaling up to full size. In an ideal world every plan would include a printed scale on it, for reference. Failing that, there might be a useful printed detail like the diameter of the wheels in inches. Sadly, this plan has neither - so we'll have to do this the hard way and work back from the fact that we know the correct full wingspan is 36" for the finished model. First, let's measure. Drag a guide to the wing tip and another to the wing root. Now measure the wing using the ruler tool, which will snap to the guides. Units need to be set to inches, not mm or pixels. Ok. The info window tells us that wing is 1.927" long. But we want it to be 18" long.
8. Ah no, wait. There is an extra complication, the Jenny has a small wing centre section in between the two main wing panels. We also need to include that in our measurements. Ok, zoom in and select an area that is the width of half of the centre section.
9. Now drag that selection area upwards and let it snap against your guide at the wing root. Now drag out a 3rd guide and let it snap to to the right hand edge of your new selection. Phew. Ok now you have some guides at the exact width of half the wingspan. All this palaver is just to help us get an accurate measurement, to scale up from.
10. Zoom out and use the ruler tool to measure the width of half the wingspan. It shows in the info window as 2.032". We need to scale that up to 18". Put those figures into a calculator to get the ratio. In this case we get 18/2.03 = 8.85
11. Keep that calculator handy. Zoom out, and take a look again at Image/ImageSize, and check the the total width of our plan in inches. That is showing as 3.67". Multiply that by our ratio of 8.85 and you get 32.51"
12. Ok. So to resize the plan, enter this data: Ignore the first 2 PixelDimension settings, they will be calculated from your settings. Set the DocumentSize to Width = 32.51", Resolution = 300 dpi, ResampleImage = 'yes' and ConstrainProportions = 'yes'. Apply that.
13. Here is our resized, full scale plan. Viewed at 100%. It's the right size now but it is a mess - we need to tidy up and get some clarity:
14. Do Image/Adjustments/BrightnessContrast to whiten the paper areas and darken the ink. This makes it really jump out.
15. Do Image/Adjustments/Posterize to 2 levels. This forces every pixel to either black or white, and eliminates all greys in between:
16. Do Image/Mode/Bitmap to 50% Threshold. This does the same as posterize. It's a belt and braces approach.
17. Zoom out and check the plan is still looking ok. Now would be a good time to clean up any dirty marks and speckles, using the pencil tool set to white. When you are done, we lastly need to export the plan as a PDF.
18. Do File/SaveAs/Format=PhotoshopPDF. This brings up a dialog box with 5 tabs. As far as I can tell, the most compact filesizes for PDF are produced by using the following settings on the first 3 of those 5 tabs: On the first 'General' tab, tick only the OptimizeForFastWebPreview:
19. On the 2nd 'Compression' tab, set Compression = ZIP and ImageQuality = 8 Bit:
20. Finally On the 3rd 'Output' tab, set ColourConversion = No and Profile = DontInclude.
The other 2 tabs 'Security' and 'Summary' can be ignored. Save.
21. Phew. All done. Go check your PDF and the filesize. Mine came out at 220KB. It's here JennyPDF if you want to have a look.
Hope that all made sense. You can email feedback to: steveWMD@outerzone.co.uk
...not finished yet. More soon. This is the first time I've tried doing a tutorial in this way.