To increase or decrease the size of an image, Photoshop uses the Interpolation method. So, for example, when you zoom in on an image, Photoshop creates additional pixels based on the values of its neighbors. Roughly speaking, if one pixel is black and the other is white, Photoshop will calculate the average value and create a new gray pixel. Some types of interpolation are fast and poor quality, others are more complex, but with the help of them good results are achieved.
First, let’s go to the main menu. Image – Image Size (Image – Image Size) or Alt + Ctrl + I.
If you click on the arrow next to the parameter Resampling (Resample Image), then several interpolation options will appear in the pop-up window:
- Automatic. Photoshop chooses a resampling method based on the type of document and increasing or decreasing its scale.
- Save details (with enlargement) (Preserve details (enlargement)). If this method is selected, the Noise reduction slider is available to smooth out noise when the image is scaled.
- Preserve Details 2.0. This algorithm gives a very interesting result of increasing the image. Of course, the detailing doesn’t become more detailed, but the one that is increasing rather strongly without losing clarity.
- Bicubic (with magnification) (Bicubic Smoother (enlargement)). A good method for enlarging images based on bicubic interpolation, designed specifically for smoother results.
- Bicubic (with a decrease) (Bicubic Sharper (reduction)). A good method to reduce image size based on bicubic interpolation with increased sharpness. This method allows you to save the details of the image subjected to resampling. If the interpolation “Bicubic, with decreasing” makes some areas of the image too sharp, try using bicubic interpolation.
- Bicubic (smooth gradients) (Bicubic (smooth gradients)). A slower, but also more accurate method based on the analysis of the color values of the surrounding pixels. By using more complex calculations, bicubic interpolation produces smoother color transitions than interpolation on neighboring pixels or bilinear interpolation.
- Neighboring pixels (clear edges) (Nearest Neighbor (hard edges)). Fast, but less accurate method that repeats the image pixels. This method retains sharp edges and allows you to create a reduced-size file in illustrations containing non-smooth edges. However, this method can create jagged edges that will become noticeable when the image is distorted or scaled, or multiple selection operations are performed.
- Bilinear (Bilinear). This method adds new pixels by calculating the average color of the surrounding pixels. It gives the result of medium quality.
Usage example Bicubic (with magnification) (Bicubic Smoother (enlargement)):
There are photos, sizes 600 x 450 pixels resolution 72 dpi
We need to increase it. Opens a window Image Size and choose Bicubic (with magnification) (Bicubic Smoother (enlargement)), units of measure are percentages.
The size of the document immediately set to values of 100%. Next, we will gradually increase the image. Change the value of 100% to 110%. When you change the width, the height will automatically adjust itself.
Now its size is already 660 x 495 pixels. Repeating these actions can achieve good results. Of course, it will be quite difficult for us to achieve perfect clarity, since the photo was small and low resolution. But look, what changes have occurred in pixels.
How big can we make photos with interpolation? It all depends on the quality of the photo, how it was made and for what purpose you increase it. The best answer: take and check yourself.
See you in the next lesson!