87. Change Image Size or Resolution
BEFORE YOU BEGIN
86 About Size and Resolution
75 Scan In Photos
88 Change the Working Area Without Affecting Image Size
As you learned in 86 About Size and Resolution , an image's size is tied directly to the number of pixels in the image as well as the relative size of the pixels. When you create images with a digital camera, or scan printed images with a scanner, you choose the resolution you want to usefor instance, 300 pixels per inch. The resolution you choose also determines the resulting print size. For example, an image that's 2,048 pixels wide by 1,536 pixels tall (the typical dimensions of an image taken with a 3MP camera), whose resolution is 300 pixels per inch, will print at 6.827" by 5.120".
So what do you do if you want your image to print at a larger size, but remain at 300dpi? In other words, what do you do if you want to increase its size without inflating the size of pixels? The answer is, you ask PSP to resample the image. When resampling is employed, either to increase an image's print size or its resolution, new pixels are inserted between existing ones. The colors for these new pixels are determined by a process that samples the values of surrounding pixels and uses estimated values in between. Resampling can also be used when reducing an image's print size or resolution. In such a circumstance, pixels are removed from an image, and the colors of the remaining pixels are determined through sampling of all the original colors and approximating their blended values.
Resample The process of creating new pixels based on the value of surrounding pixels.
Because resampling is based on best-guess estimation, using it to change an image's size or resolution by more than 20% often produces poor results. You can resize or change an image's resolution without resampling by telling Paint Shop Pro that you want to maintain the relationship between the size and the resolution. In this manner, you can double an image's print resolution by cutting its print size in half. The image will contain as many pixels as it did before, but the pixels will be smaller, and there will be more of them per inch. Onscreen, you won't see any change at all.
87. Change Image Size or Resolution
One fast way to remove moir ƒ patterns, fuzziness , and spots from an image is to scan the image at 600dpi and then reduce its resolution to 300dpi while maintaining its print size .
Display Resize Dialog Box
Choose Image, Resize from the menu bar or press Shift+S . The Resize dialog box appears.
| | Stop Distortion
If you do not want the image distorted during the resizing process, select the Lock Aspect Ratio
option to turn it on.
If the image contains multiple layers, and you want all the layers resized to the same size, enable the Resize All Layers
option as well.
If you don't choose the Resize All Layers option, only the current layer or active selection is resized. Leaving this option disabled is a handy way to resize a selection or an image copied to a new layer.
| | Turn on Resampling
To have PSP estimate colors for pixels when you change the print size or resolution, enable the Resample Using
option and select a sampling formula from the list. Typically, the Smart Size
option works best because it determines the appropriate formula based on the image's unique requirements. Here's a brief description of the other formulas:
- Bicubic Estimates each new pixel's color value based on the values of the 16 nearest pixels to the new pixel's location relative to the original image, in a 4x4 array. This method is best used when enlarging an image.
- Bilinear Estimates each new pixel's color value based on the values of the four nearest pixels to the new pixel's location relative to the original image. This method is best used when reducing an image.
- Pixel Resize Copies the color value of each new pixel from the exact value of its nearest neighbor. Fast and dirty, with often poor results including jagged edges and stair-step effects.
- Weighted Average Estimates each new pixel's color value based on the values of all the pixels that fall within a fixed proximity of the new pixel's location relative to the original image. Here, the pixel residing in the same proportionate location in the original image as that of the new pixel in the resized image is given the extra "weight" when estimating the new color value. This method is best used when reducing the size of an image.
To avoid resampling an image, turn off the Resample Using option and change either the Height/Width or Resolution values in the Print Size area of the Resize dialog box. If you increase the Resolution without resampling, for example, the image will be resized smaller.
Select a New Size and/or Resolution
If you know what size you want the final image to be, type a value in the Print Size Width box; the Height value changes proportionately (or vice versa).
You can also change an image's size by adjusting its pixel dimensions. For example, if you want the image to be twice as big, select Percent from the Pixel Dimensions list and type 200 in the Width and Height boxes. This changes the number of pixels without affecting their size ( assuming Resample is on).
To change the resolution, type a value in the Resolution box. Altering resolution in this manner does not change the image's print size, unless you entered new print dimensions earlier. Because the Resample Using option is selected, new pixels are created as needed to meet your print size and resolution requirements.