Magnfication in Windows Picture and Fax Viewer doesn't really show more detail, it merely pixelizes the image. I've heard of and seen demonstrations of interpolation on the internet but I have no way of using it on pictures that I want to enlarge to get
a better look at a small detail.
When will there be an option in Windows Picture and Fax Viewer to interpolate the image?
My guess is Longhorn.
It can't show more detail if there's no more detail in the image. Once you expand a bitmap past its natural size, you will inevitably see a less clear image. Interpolation won't help you - that's just a fundamental limitation with bitmaps.
Interpolation doesn't show more detail. It is simply the process that happens when you take an image and enlarge it. If you enlarge a bitmap, you're trying to make it fill an area with more pixels than the image has, so you have to add some extra pixels to
make the image large enough. The process of inventing these extra pixels to fill the space is called interpolation.
The simplest interpolation style just replicates pixels, and that leads to the blocky 'pixellated' images. (Depending on your definition, you might not even regard this as interpolation, since it doesn't really invent any new pixels, it just duplicates existing
More sophisticated interpolation schemes try to make a better guess at what would be in those extra pixels if they had been present in the original image. This tends to involve deriving a mathematical function which matches the original image, and then using
that function to fill in the blanks. Biiinear and bicubic interpolation are the most common.
As it happens, Windows Picture and Fax Viewer does use interpolation. (At least it does on Windows XP - what are you using?) Not sure whether it's bilinear, bicubic or something else, but it's definitely not doing straight pixel replication.
The fact is though, that regardless of what interpolation scheme you use, if you expand things enough you're going to hit a fundamental limit: interpolation can't recover detail that wasn't in the original image to start with. It can only work from the pixels
in the source image. So with any interpolation scheme, if you expand the image enough you're eventually going to see the pixels in some form or other. Interpolation can merely smooth out the edges a bit. It can't magically recover microscopic detail from an
image taken with a crummy 200x200 pixel mobile phone camera.
More sophisticated interpolation schemes try to make a better guess at what would be in those extra pixels if they had been present in the original image. This tends to involve deriving a mathematical function which matches the original image, and then
using that function to fill in the blanks. Biiinear and bicubic interpolation are the most common.
This sounds like what I have seen, which made me think that sophisticated schemes were interpolation and simple pixel copying methods were just magnification, zooming or enlargement.
This is what I would like to see in Windows Picture and Fax Viewer one day.
An example showing the existing interpolation in the picture viewer in XP. This is sunset.jpg one of XP sample images magnified to 800x in Paint and Image Viewer.
You're right, I never noticed... I guess I should now be asking if Microsoft is going to look into developing it further.
Consider a bitmap which is a series of 1 pixel wide vertical lines alternating between white and black. What should the interpolated image look like?
Considering that this application is a fax viewer (and faxes are often made up of black and white pixels using CCITT compression), it is surprising that they would choose to interpolate, in my opinion.
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