Tuesday, November 16, 2010

Triple T Tuesday - Resizing vs. Resampling

Resize or Resample? That is the question.

Here is the textbook version.
Image Resizing: Changes the size that the image will print without changing the number of pixels in the image.
Image Resampling: Changes the number of pixels in the image.
Clear as mud? No worries. I'll demonstrate by showing you the difference between resizing and resampling.

First, grab a photo in Photoshop to play with. Here is the one I am going to be using.

Let's check the stats on the image.

1. Click open the Image Menu at the top of the screen.
2. Select Image Size from the drop down menu.
The Image Size box is divided up into two main sections.
3. The Pixel Dimensions section shows the width and height of the image in pixels. It also shows the file size of the image.
4. The Document Size section shows the print size based on the image resolution.
5. There are two more options in the Image Size dialog box below the Document Size section:
  • Constrain Proportions: This links the width and height of the image together to prevent distortion. If you make a change to the width of the image the height will change automatically, and vice versa.
  • Resample Image: This is the option that determines whether you are resizing the image or resampling it. Resizing leaves the pixel dimensions the same and changes the size that the image will print, while resampling physically changes the number of pixels in the image.

From the image above you can see that when Resample image is unchecked the Pixel Dimensions section of the dialog box is not functional. At this point the only editing option is to change how large the image will print using the Document Size section.
Notice too that the Constrain Proportions option at the bottom of the Image Size dialog box is grayed out when Resample image is not checked.

When Resample image is checked you can now edit the information in the Pixel Dimensions section. You may edit the image by changing the pixel properties as well as the Document Size. Notice too that as the information is edited the Pixel Dimension information changes as well.

Here are the images after editing close to each other for comparision. The first image is resized, while the image have been resampled. There is not much of a noticeable difference in the image at this point, other than the size.

Here are the images zoomed in close. Again, the first image is resized, while the second image is resampled. By viewing this close you begin to see the difference in the two images, as the second image is much more pixelated than the first.

I also wanted to touch briefly on transforming an image without distortion. There are times when an image needs to be transformed to fit in a frame or maybe a frame transformed to fit an image. Either way, there is a way to edit an image without causing distortion.

1. To transform an image click on Edit.
2. Then scroll down and select Free Transform (or try using one of my favorite shortcuts Ctrl + T).
3. The layer that is selected will be surrounded by a border with nodes. From this point you can manipulate the selected item. You can squeeze it down to the size that you like. This "freehand" style of transforming usually causes the distortion. A more "controlled" style of transforming occurs when you select one of the nodes and hold the shift key while manipulating the image.
4. Once the correct size is achieved click on the check button to confirm the change.

Above are examples of the images that have been transformed. The first image was edited using a free transform, while the second image was edited using the controlled transform (holding the shift key while adjusting). You can see that the first image looks distorted. It is best to transform an image while holding the shift key so that the item being adjusted does not get distorted.

Oh... Before I go. I wanted to also mention that today is $1 Pixel day at Gotta Pixel. Here are the items in the $1.00 bin for today only. Keep looking as there is also a coordinating freebie below.

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