Image > Resize
The Resize command allows you to enlarge or reduce the physical size of the image by changing the number of pixels it contains. It changes the size of the contents of the image and resizes the canvas accordingly.
1. Do one of the following:
 Choose Image > Resize
 Click the Resize button on the toolbar
2. Use the following options:
Choose the units of measurement. You can select between Pixel, %, Inch and Centimeter.
Keep aspect ratio
Use this option if you want the image width / height aspect ratio to be fixed during resizing. If this option is checked, then typing a new Width value will maintain a proportional Height value, and vice versa.
Interpolation is an imaging method to increase (or decrease) the number of pixels in a digital image. How smoothly images are enlarged depends on the sophistication of the algorithm.
Nearest Neighbour
Original 25%Nearest Neighbour
Nearest Neighbor Interpolation is the simplest method and basically makes the pixels bigger. The color of a pixel in the new image is the color of the nearest pixel of the original image. If you enlarge 200%, one pixel will be enlarged to a 2 x 2 area of 4 pixels with the same color as the original pixel. Most image viewing and editing software use this type of interpolation to enlarge a digital image for the purpose of closer examination because it does not change the color information of the image and does not introduce any anti-aliasing. For the same reason, it is not suitable to enlarge photographic images because it increases the visibility of jaggies.
Original 25%Bilinear
Bilinear Interpolation determines the value of a new pixel inspired by a weighted average of the 4 pixels in the nearest 2 x -2 neighborhood of the pixel in the original image. The averaging has an anti-aliasing effect and therefore produces relatively smooth edges with hardly any jaggies.
Original 25%Bicubic
Bicubic Interpolation is a more sophisticated interpolation method and produces smoother edges than Bilinear Interpolation.
Resize all layers
This option allows you to resize the background layer and all other layers.
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