I've read many posts in regards to this subject which still leave me wondering as to what the best approach is.
I have 96 DPI BMP's that measure 816 W X 1344 H. I want to bump these to 200 DPI but try to maintain quality/aspect ratio for onscreen viewing and printing.
Generally you can think of DPI as nothing more than advice to the printer on the size to print the image.
So if you change the DPI of an image from 96 to 200 without changing the resolution (pixel size) it will print at half the size (presumably with slightly better quality).
If you scale the image and change its DPI from 96 to 200, you will get basically the same output as the original.
So, I guess the question is, what are you trying to achieve by updating the DPI?
I'm trying to do the latter...I think. The problem arises from users using new tablet machines. The saved 96 DPI BMPs print at 1/4 the size of older laptops. The display of the BMP is impacted as well, (smaller) but less dramatically. I want to fix the problem on these new machines without breaking how it is displayed on the older machines...which I guess means I have to detect the display properties and react accordingly.
Generally computers and other devices should ignore DPI for display (using only the pixel size to decide its display size). I'm surprised if you are seeing something different.
Of course it is often used when printing. You set the DPI to 48 (without scaling) to print the image at twice the size. This should not affect the quality (because the image data itself has not changed).
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Changing Image Size
Posted - Apr 28 2017 : 13:35:43
