Everything in the picture is clear. lower quality for increasing size of picture is acceptable Because the new pixels must be created but how about reduce size of picture?

why? and does it possible to make image smaller without reduce quality and without redesign it?

enter image description here

  • Can you specify which method (or methods) did you try to reduce the image? That might also make a difference in the quality. – Luciano May 6 '16 at 13:44
  • Ctrl+Alt+I (image size) / I only changed width and height. – Ayub May 6 '16 at 13:59
  • This is why we use vector images. But yes the choice of interpolation algorithm plays a huge difference here. – joojaa May 6 '16 at 15:00

Since there can be no half-pixels, when you reduce a 5x5 pixel grid by 50%, you must make a decision how to render 2.5 x 2.5 pixels.

In your example, the chimney width is not evenly divisible by 2, so you get a precision error. In the angled roof, I think one might refer to this as a quantization effect: a squaring off of a smooth function.

  • redesigned version has also the chimney but we don't have any lost in quality? – Ayub May 6 '16 at 14:09
  • lost from what? you redesigned it at 50 x50 px. How can it lose anything. It was not resized. – Yorik May 6 '16 at 14:12
  • please replace a home icon with x*y px (odd) rectangle shape and after that resize it to 50*50px, You will see that we'll not have any loss in quality. I couldn't figure out what is your meaning. – Ayub May 6 '16 at 15:23
  • Lets look at your example again. The chimney in the reduced-size one is thinner, proportionally, than the chimney in the original. This is because the new smaller chimney width, when calculated, was not an integer. When rounding to the nearest integer, the width was made smaller and it now looks distorted when compared to the original 100x100 size. – Yorik May 6 '16 at 15:42
  • Not only the thickness but sometimes the position of the edges of an object might fall in an fractional pixel coordinate, so it will be distorted even when the width is an integer. – Luciano May 6 '16 at 16:06

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