1949 Oldsmobile Shop Manual online

The "Oldsmobile 1949 Shop Manual 6 and 8" is now online at http://edge-op.org/1949_Oldsmobile/

No copyright renewal record was found for this book, so it *should* be in the public domain. If I missed a renewal record somewhere, I hope GM just does a cease and desist.

The manual was unbound and scanned at 600 dpi. Those giant images were then copied, converted to jpg and resized for the web. Detailed and rotated images were created from the originals using Gimp.

Discussion of the process is at http://www.hotrodders.com/forum/old...ning-96976.html

It was a pita to do but maybe somebody will get some good out of it.

If you know anyone associated with tocmp.com please let 'em know about this. They may want the original scans as well as the jpgs on my website.


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I've added this to the General Rodding Tech Technical Data category of the Hotrodders Knowledge Base.

And, I've just PM'd khardy, a member of our forums who works on The Old Car Manual Project.

Also, I noticed that you were using GIMP. I could use some advice on reducing JPEG filesize without significantly compromising image quality. Keep in mind that image editing is probably my weakest skill.

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Cool! Thanks!



He posted a message in the thread in the Lounge, but I remember someone telling me his work takes him away for extended periods of time. Hopefully, he'll have time to copy those images onto tocmp.com where more people will find them. Just like family photos, the more they are passed around, the less likely they can ever be lost.



I love GIMP, even though I can't use a quarter of the stuff it provides. It doesn't mind that I'm not an artist.

JPEG file sizes are mostly dependent on the resolution and, to a much lesser extent, quality settings. Resolution includes the image size, pixels per inch or millimeter and the color depth (which includes grayscale bits). You can get the image info in GIMP by choosing View=>Info Window. For example, the cover page http://edge-op.org/1949_Oldsmobile/images/000.jpg yields this information:

Pixel dimensions: 800 x 1031 pixels
Print size: 33.90 x 43.69 millimeters
Resolution: 23.6 x 23.6 pixels/mm
[...]
Visual depth: 24

23.6 pixels/mm is 599.4 pixels/inch. The dimensions of that image are about the same as those found on tocmp.com but the resolution is about triple, so the file size is triple. The reason for using that high resolution was so that these images could be zoomed quite a bit without loss of detail. That can compensate for my lack of experience in scanning manuals, which may have caused me to choose badly in deciding on the illustrations that needed extra images.

The visual depth, 24, is simply the bits for each of the red, green and blue channels. This image uses 8 bits for each.

GIMP doesn't show the JPEG quality in its "Info Window", but allows you to choose that when you use 'File=>Save as' or 'File=>Save a copy' and use a filename extension of 'jpg', 'jpeg', or 'jpe'. The quality setting is all about eyes. It's not a precise determinant of file size, simply because it's not a quantizer but rather a number for an algorithm to use when deciding what to lose. Given two identical images, the quality value will make a difference in the file size.

Generally, using 100% quality on a JPEG is a waste. If you need the image to be that precise, you probably need a lossless format. 75% gives an image that will look right to most people, that is, a reduced size image of that quality will appear to be a correct representation of the original. The more you zoom, the more of the losses that were incurred in the reduction will begin to become apparent.

There is a good discussion of JPEG quality at http://photo.net/learn/jpeg/

JPEGs compress well. The 000.jpg image shows up as 6.33 MB in memory while the file occupies 231 KB. PNGs also compress well -- the original scan, 000.png, occupies 255 MB in memory while the file size is 74 MB. Note the different ratios there: 27.4 versus 3.445.

Choose the image format according to your end purpose -- JPEG is great for photos, PNG preserves the dots you put into it regardless of appearance. Choose image size (WxH), resolution (dots per inch or dots per mm) and color depth. If it's a web image that isn't going to be blown up and printed, 72 - 75 dpi is plenty. If it might be blown up and printed, up to 300 dpi makes sense. If it may need to go through OCR, 600 dpi helps, according to Project Gutenberg. If it's for a glossy photo, every dot you can squeeze into every inch, up until your computer goes comatose, will likely be less than the grains on a film photo. (35 mm film can resolve to about 6000x4000 to 9750x6500, or about 24 to 64 megapixels. Kinda makes 6 MP cameras look weak.)

To see more information about an image than most people ever want, open it with 'display' from ImageMagick, left click on the image to pop up the menu, and choose 'Miscellany=>Image Info'.