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SBT · 07-02-2013, 05:14 AM

What I do:

When using Internet Archive, select 'Read online'.
If I want to save a page with an image, I right-click on the page, and select 'open in new tab'.
The image is loaded with an URL like http://ia700300.us.archive.org/BookReader/BookReaderImages.php?zip=/30/items/underredrobe00weymiala/underredrobe00weymiala_jp2.zip&file=underredrobe00 weymiala_jp2/underredrobe00weymiala_0006.jp2&scale=2&rotate=0
Change scale=2 to scale=1, and you get max resolution.
Right click on image, select 'copy image'
Open Gimp
Press Shift+Ctrl+V, aka. 'Edit->Paste as -> New image'
Set 'Image->Mode->Grayscale'
Set zoom to 100%.
Observe that in this case there are dots (rasterization?) in the image. They mess up image sharpening, we remove them by 'Filters->Blur->Gaussian Blur' ,blur radius 2x2 pixels.
Set zoom to 25% again.
Select 'Colors->Levels'
In the Popup window, slide the white triangle below the histogram to the left until the paper margin in the picture is white, i.e. to the left of the right-hand peak in the histogram.
Slide the black & mid-level triangles until you are satisfied with the result, and click OK.
Select 'Filters->Enhance->Unsharp Mask'. This filter accentuates borders between dark and light areas, so it actually sharpens the image.
Use default values (5.0, 0.5, 0)
Undo & fiddle with values if result is unsatisfactory, or just skip the unsharp filter.
If you have wavelets installed in GIMP, you can use it to mitigate the effects of unsharp again When the image is a bit 'blobby', as in this case, wavelets can smooth things a bit. Apply 'Filters->Enhance->Wavelet denoise', in this case Threshold=0.75, Smoothness=0 are sensible values.
Select 'Tools->Selection tools-> Rectangle select' and select the image part of the page.
Select 'Image->Crop to selection'
Now I save the full-size image.
Select 'Image->Scale image', and shrink it to whatever size you want for your book.
Select 'File->Export'.
For images like this, which are slightly fuzzy and blurry, I often set jpeg quality to ~70%.
Line drawings I normally save as png, but first I select
'Colors->posterize' and set levels=16 (Even on colour screens, fifteen shades of gray normally suffice, and it makes for really small file sizes)

The raw/jp2 images are even larger and more detailed, but In my experience there wasn't anything to be gotten by using them instead. Also, they are often not yet aligned, so you'll have to rotate them a bit as well.
When there are many images in a book, I use the Internet Archive thumbnail viewer, note down the page numbers of images, and make a shell loop to retrieve the relevant pages. This is left as an exercise for the reader

07-02-2013, 05:14 AM	#12
SBT Fanatic Posts: 580 Karma: 810184 Join Date: Sep 2010 Location: Norway Device: prs-t1, tablet, Nook Simple, assorted kindles, iPad	What I do: When using Internet Archive, select 'Read online'. If I want to save a page with an image, I right-click on the page, and select 'open in new tab'. The image is loaded with an URL like http://ia700300.us.archive.org/BookReader/BookReaderImages.php?zip=/30/items/underredrobe00weymiala/underredrobe00weymiala_jp2.zip&file=underredrobe00 weymiala_jp2/underredrobe00weymiala_0006.jp2&scale=2&rotate=0 Change scale=2 to scale=1, and you get max resolution. Right click on image, select 'copy image' Open Gimp Press Shift+Ctrl+V, aka. 'Edit->Paste as -> New image' Set 'Image->Mode->Grayscale' Set zoom to 100%. Observe that in this case there are dots (rasterization?) in the image. They mess up image sharpening, we remove them by 'Filters->Blur->Gaussian Blur' ,blur radius 2x2 pixels. Set zoom to 25% again. Select 'Colors->Levels' In the Popup window, slide the white triangle below the histogram to the left until the paper margin in the picture is white, i.e. to the left of the right-hand peak in the histogram. Slide the black & mid-level triangles until you are satisfied with the result, and click OK. Select 'Filters->Enhance->Unsharp Mask'. This filter accentuates borders between dark and light areas, so it actually sharpens the image. Use default values (5.0, 0.5, 0) Undo & fiddle with values if result is unsatisfactory, or just skip the unsharp filter. If you have wavelets installed in GIMP, you can use it to mitigate the effects of unsharp again When the image is a bit 'blobby', as in this case, wavelets can smooth things a bit. Apply 'Filters->Enhance->Wavelet denoise', in this case Threshold=0.75, Smoothness=0 are sensible values. Select 'Tools->Selection tools-> Rectangle select' and select the image part of the page. Select 'Image->Crop to selection' Now I save the full-size image. Select 'Image->Scale image', and shrink it to whatever size you want for your book. Select 'File->Export'. For images like this, which are slightly fuzzy and blurry, I often set jpeg quality to ~70%. Line drawings I normally save as png, but first I select 'Colors->posterize' and set levels=16 (Even on colour screens, fifteen shades of gray normally suffice, and it makes for really small file sizes) The raw/jp2 images are even larger and more detailed, but In my experience there wasn't anything to be gotten by using them instead. Also, they are often not yet aligned, so you'll have to rotate them a bit as well. When there are many images in a book, I use the Internet Archive thumbnail viewer, note down the page numbers of images, and make a shell loop to retrieve the relevant pages. This is left as an exercise for the reader Attached Thumbnails Last edited by SBT; 07-03-2013 at 04:49 AM. Reason: Expanded with images ++