Converting PDF Files to .JPG Files

Q. Can I use a graphics program I already have to convert PDF files to JPG files?

A: If you are lucky your graphics editor software will do the conversion.  I use Corel Paint Shop Pro and it works fine.  The only caveat is that when it is imparting the JPG file, it defaults to a resolution of 72 DPI (Dots Per Inch) which is way too course.  Use 200 DPI for smaller maps and 300 or even 400 for larger ones.  Microsoft Paint that comes free with windows will not do the conversion but Paint is doe to get a major revision with the 2017 update to Windows 10 and it may be able to do it then. If you do not have a program that will do the conversion, GIMP, currently GIMP 2.8 at http://www.gimp.org/ Is a free program and very good at converting between various graphics formats including from .PDF to .JPG. It is a full featured image editor program but I only use the file conversion feature. I have no knowledge of the other features.

Q. What are some other options?

A: If there is not a lot of detail in the map, you can use the Adobe Acrobat Reader Snapshot feature. Click Edit, then take a snapshot, then click on one corner of the area you want to capture then move the mouse to the opposite corner holding the mouse down.  When you release the mouse, the area highlighted will be copied to the clipboard. Then past it into Maprika with File>New From Clipboard.   Note, there is an option to copy all.  Sometimes that works fine but other times it does not get all the layers in the image.  Either way, you get less detail than by using a program like Gimp.

Q what if the map has a lot of detail?

A: Use another program.  Your usual photo editing program might be able to read the .PDF file.  I use Paint Shop Pro and it will unless there is some extra protection coded into the image.  On an iPhone, you can use a free app called PDF to Images by Miles Jordan Software.  It is a little tricky to use.  You find the web site with the .PDF file you want, I use Safari, Google does not seem to work with this app. Then tell Safari in my case to "Open In" "PDF to Images" unfortunately I could not do this again while I am writing these notes.  I am not certain what i am doing wrong.  At any rate there are a number of free and pay programs in the apple store to do this job.  I would always recommend doing this operation on a desktop if you have one available.

Q: What about using GIMP?

A: Gimp is particularly powerful but confusing to use. The current version is GIMP 2.8 and is available at http://www.gimp.org/ It is a free and very good at converting between various graphics formats including from .PDF to .JPG. It is a full featured image editor program but I only use the file conversion feature. I have no knowledge of the other features.
There is also a Mac version at: http://gimp.lisanet.de/Website/Download.html.  GIMP works for me when my regular photo editor tells me I need a password to read the JPG file.

It is not as strait forward as it might be.
To load the file into GIMP use FILE>OPEN then find the .PDF file you wish to open.
You then are presented with a "Import from PDF" window where you define the size of the image you want to map the PDF file onto. This controls the resolution.
I typically use 2000 for the larger dimension leaving the other and Resolution alone. The Resolution setting is only used if you choose to print the image out in its "original" size so I just leave that at the default. If the map has lots of detail, like the map of bike trails covering the western third of my county, they use a bigger number like 6000. 
Then click on IMPORT.
To save the image as a JPG file, FILE>EXPORT AS then give the file a name ending in .JPG instead of the default ending is .PDF
Then click EXPORT. A dialog window will open asking what quality you want. This is basically how much you want the file compressed. Feel free to just use the default.  I found that using more compression did not result in a smaller file by the time I got dun processing it in Maprika.  The default directory is the one you read the file from.

Another trap with GIMP is if you want to go back and try reading the image with a different resolution or even a  different image, you have to close the program and restart it or it will just read it with the old resolution.  (Of course some times that would be fine.)
Once you have converted it on your desktop, just mail it to your smart phone and save it in with your pictures (on your Camera Roll) if you want to process the picture there or do what I do an process it through Maprika on your PC.

Q: What is the optimum file size? (If you are just getting  started you can ignore this and just go with the general recommendations.)

A: I have found that the .JPG file needs to be at least .5 Meg (500 Kb) I typically save .JPG files with a compression factor of 20%, a fairly low compression rate. If you do not understand this just go with the default. Some images such as ones that are only 640 by 480 are only about 0.07 Meg. These sort of files do not have sufficient detail. The big problem with these small files is that Maprika cannot zoom in very far. The fix to this problem is to read the file in to some picture manipulation program. On the program I use the commands are: IMMAGE > RESIZE > Then put in something like 2000 pixels for the longer dimension.  If the files get really big, then Maprika cannot process them. It will just quit without an error message. Making the file smaller with more compression will not help. It seems to max out on the number of pixels. If you really need a large file, then process it on a PC. That is now my preferred method for all files anyway as long as it is a file I can make public as you have to upload the file to Maprika to get it on to your smart phone.  Try to keep the file size under 2 Megs but you can get away with 3+ if you really need it.  If your file size is too small, when you zoom in on some detail like a street name, you will see the text pixilated.  If you see this just repeat with a larger size.

A good scale is something like 600 pixels/Mi or 400 pixels/KM if you are covering a moderate sized area like a ski area or city center.  However I did get away with  only 150 pixels/Mi for a bicycle map that covered about 40 miles by 50 miles.  If I had used 600 pixels/Mi the file would have been 13 Megabytes.

There are some examples of much bigger maps on their web site. The Mt Rainier Topag map is 27 MB so if you really need the size, you may be able to get away with it.  You would definitely need to build the GPS enabled map on a PC.

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