Here’s a puzzler transform problem

DS
Posted By
David_Skidmore
Oct 9, 2005
Views
261
Replies
4
Status
Closed
Make an 8×10 300 dpi document.
On a new layer make a precise 5×7 invertically oriented selection Fill the selection with any dark color (past midtone)
Scale that 5×7 rectangle (on the second layer) to precisely 3.5 x 5 in (use the input boxes to input 3.5in and 5in)
Now closely magnify (down to the pixel level) and notice that there is a narrow lighter color band around the outside of what should be a perfectly solid image.

Why is that?

Why should the scaled image not be precisely the same as the larger.

dc

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Y
YrbkMgr
Oct 9, 2005
Why is that?

Rounding of Pixel values resulting in antialiasing? I didn’t actually go through the procedure to look, but that’s my first thought. The mathematical rounding of pixels can cause anomalies.
CC
Chris_Cox
Oct 9, 2005
….because the bicubic resampling kernels have some inherent sharpening in them, and you resampled the image when you did the free transform.
JR
John_R_Nielsen
Oct 9, 2005
So, using Bi-linear or Nearest Neighbor makes it work the way it ought to?
CC
Chris_Cox
Oct 10, 2005
No, it’s already working the way it should.

Nearest Neighbor will lead to really poor quality, but does use just the original colors. Bilinear won’t have overshoot, but will lead to more blurring and lower quality than bicubic kernels.

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