Preview - scanning resolution

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Level 1

44 points

Preview - scanning resolution

When downloading documents to my desktop I frequently get a lot of black image around the text.

I know I can remove that quite easily - these docs are usually in .jpeg format and to remmove the black surround it has to be first converted to a .png format.

After removing the blackness, I usually then select the image (cmd+shift+4) which takes the image to the desktop as a png. However when comparing the new image to the older one, using Preview, I cannot zoom in very far before it pixalates and goes out of focus.

I think it may have something to do with the resolution settings within preview.

Does anyone know how and where I can change these settings?

or

alternatively what is the best way to preserve the images so I can zoom right in without pixalisation?

Alan

Posted on Feb 28, 2013 12:56 AM

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Answer 1

Mar 1, 2013 3:22 AM in response to ribbo39

Once you take a screen shot (cmd shift 4) you are essentially taking a picture of your screen.

Please forget doing this as this is not how you crop an image in preview.

The best way to go about doing this is to use your scanner to crop the appropriate area before it scans. Most scanners can do this with the included software.

if this is not an option, then use preview to crop your image.

expand preview all the way out so you see these tool options on the upper right corner of Preview.app.

first click the box with the dots (the one on the left) to select the area you want to crop. Then select the second circled option that looks like two right angles merged together to crop the image to the selection you just made.

now save.

What you were doing is taking a screen shot.

taking a screen shot has a resolution of 72dpi and should be used to trouble shoot issues or show someone something on your screen, like I have done with this example.

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Answer 2

ribbo39 Author

Level 1

44 points

Mar 3, 2013 1:24 PM in response to TheSmokeMonster

Hi TheSmokeMonster,

Thanks for you reply and sorry for delay in getting back to you.

What you have suggested works very well apart from one aspect. If the document is not square or rectangular then parst of the image are deleted. Here attached is a part of the document showing an area - hopefully it will fit.

The other point; is it possible to change the resolution in a screenshot from what you say is 72 dpi?

User uploaded file

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Answer 3

Mar 3, 2013 7:33 PM in response to ribbo39

Images can only be rectangular. Even with screen shots, that's the case.

What about cropping an image this way doesn't work for you? I didn't see the attachment.

No, 72DPI images can't be upscaled, or enhanced, that's only in the movies. What would happen is you blow up an image and it's pixels, making for a really jagged looking image because it can't re interpret the information.

Having said that, photoshop is pretty good at raising the DPI with less sacrifice to the image.

I'm glad I could be helpful.

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