The following was posted last time you reported the same non-error...

If you look at the 99% size image in isolation, you'll see that it has uniformly distributed slight blurring due to resampling.

When it's overlaid at 50% opacity on the original (or vice versa), you are seeing an additional blur due to features in the two images being offset. Obviously, the offset, and therefore its blurring effect, linearly increases from zero pixels at the centre to several pixels (depending on image size) at each corner.

Here's a 100% size original followed by the original overlaid with a 90% reduced duplicate at 50% opacity. You see the offset increasing as the distance from the centre increases.

222design wrote:

 

It should be blurred evenly. The area that the pixel covers should have an equal offset whether it is in the centre or on the outside.

Lets try again.  Try this approach. start by not moving any pixel center and resize every pixel to 99% of its size. You wind up with an image with gaps between pixels. 

Now lets eliminate these gaps.  Start from the center. Move the pixels around the center pixel in one gap distance. next move out and move the surrounding pixels in two gaps repeat move in three gaps etc...

This is how Image size works when RESAMPLE is not checked and you increase the image's DPI resolution.  Print pixels are smaller the number of pixels remain the same and the print size is reduced in size.  The higher resolution increases the image sharpness.

Scaling an Image width and height by the same percentage should be liner be it done by changing pixel size or interpolating the number of pixels in the image.  When resampling an image's image quality will suffer for the new pixels are computer generated using some interpolation method. Not captured with optics and a sensor.  Pixel quality of a resampled image will not be as good as the pixel quality of the original image.

222design wrote:

 

Yes but this is incorrect. When you change the layer size to 99% it resamples the image producing a different grid of area covered by a pixel. It doesn't matter whether the pixel is at the centre or the edge the offset will be the same, so the image should be evenly blurred.

Your thinking is incorrect.

The offset must increase as the distance from the scaling origin is increased. There is no possible other outcome. The blur therefore will increase with distance from point of alignment of the stacked images.

Consider the scaling in one dimension to simplify matters.

Here's an original row of squares and a copy at 100% scale.

Now the copy row has been scaled to 99%. See the offset increase from left to right.

Finally, when overlaid, there is the explanation for the blur not being contant across your stacked layers.

The images are demonstrating what you saw in your own stacked image, yes, but there is no error. You'll help your argument that there is an error in Photoshop's scaling if you post an example of "correct" scaling which conflicts with Photoshop's scaling.

222design wrote:

 

how can I post an example of correct scaling with photoshop when photoshop has the scaling error in it?

You make a mock-up of the result which you consider correct.

There is an error in your images as they are done with photoshop and photoshop has this error in it.

You have yet to demonstrate that.

You surely know your own expectation of my row of squares when resized to 99%. That can't be difficult to illustrate.

conroy wrote:

 

You surely know your own expectation of my row of squares when resized to 99%. That can't be difficult to illustrate.

Ok, I'll illustrate what 222design expects

the black lines represent the pixel grid in Photoshop. The blue squares fitting in each pixel represents the pixels of the original image. The small red squares is 222design's expectation of scaled image that will produce an even blur.

@ 222design, the problem with your expectation is that it is not possible for a pixel to be smaller than a cell of the pixel grid, and as explained many times before there will be always one center of scale for all pixels. It is not possible to scale each pixel individually from its own center.

so, the following statement is incorrect:

222design wrote:

 

....When you change the layer size to 99% it resamples the image producing a different grid of area covered by a pixel. ..

the pixel grid never changes, it is absolute.

222design wrote:

 

yes I know that the pixel grid never changes and as I have stated what does change is the area covered by the pixel and this should be a constant offset giving a constant blur....

And because the grid never changes but only the area covered by the scaled pixels, the only possible ways for this to happen are illustrated on the images below. The blue pixels show where the burring will occur and cannot be the same for all pixels.

222design wrote:

 

the resampling is the same at the edges and at the centre it is linear or uniform so it should be constantly blurred.

There are two sources of blur in your example of an overlaid image of different scale and 50% opacity. Maybe you missed me telling you that last month and earlier today:

"If you look at the 99% size image in isolation, you'll see that it has uniformly distributed slight blurring due to resampling.

When it's overlaid at 50% opacity on the original (or vice versa), you are seeing an additional blur due to features in the two images being offset. Obviously, the offset, and therefore its blurring effect, linearly increases from zero pixels at the centre to several pixels (depending on image size) at each corner."

222design wrote:

 

but the resampling to 99% is linear, it does not matter whether it is an outer or inner pixel, so the offset is constant, so it should be uniformly blurred.

The main blur that you are seeing, the one that increases toward the outside of the image, is not a resampling blur, though. It is a perceptual blur due to offset of features in the differently scaled stacked images. Even if the images were composed of an infinite number of infinitely small pixels and the resized one had no resampling blur, the offset due to scaling would still result in you perceiving a blur that increases from zero at the centre to maximum at the corners.