CS 105 Lab 2 --- Fall 1998 -- Resizing the Image

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Go forward to Saving Your Image as a JPEG file

Resizing the Image

This is it, the last step. Actually this is two steps in one. You will complete your work by resizing the image and adjusting its resolution.

You may recall that this image is stored using 300 pixels per inch. This is much higher than what most monitors can display. For printing, 300 pixels per inch might be appropriate, but for screen display in a web browser 72 pixels per inch is better and requires far less transmission time.

Adobe Photoshop combines the setting of image resolution with image size so we will take care of both now.

Select the "Image size" item from the "Image" menu. The dialog box you examined at the beginning of this tutorial should appear.
At the bottom of the dialog box there is a check box asking whether PhotoShop should resample the image. Make sure that this is checked. If it is not, PhotoShop will not let you change the number of pixels used to represent the image.
Also make sure that "Bicubic" is selected as the resampling method. This is the method PhotoShop will use to generate the new set of pixels used to represent the image after resizing.
Finally, make sure that "constain proportions" is selected. This will ensure that the length and width of the final image remain in the same proportion as in the original.

To understand the importance of asking PhotoShop to resample, consider the following example. If you took a 3x5 photo encoded at 300 pixels per inch and resized it to be a 6x10 without resampleing, Photoshop would have to change the resolution of the image to 150 pixels per inch. On the other hand, if you did the same resizing operation allowing resampling, Photoshop would quadruple the number of dots used to represent the picture. The colors of the added dots would be "made up" by Photoshop by interpolating from the colors of the pixels of the original image.

At this point, the actual size of the image in inches is rather small. Increase this size by making its width 4 inches. Notice that because the image's proportions are fixed, the height changes when you change the width.
Next, to reduce the resolution of the image to something appropriate for a web page, replace the "300" pixels per inch by "72".
Notice how the measurements of the image in pixels changes as you do this.
Click OK.