An image processing session

Skills: change view (zoom in or out), rotate, select a portion, crop, resize, change contrast, filter, compress

IT concepts: image processing operation

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

Where does this topic fit?

• Internet concepts– Applications– Technology– Implications

• Internet skills– Application development– Content creation (images)

Selected image processing operations

• Rotate an image • Crop an image• Change image contrast• Apply a filter to an

image• Resize an image• Select a portion of an

image

Let’s apply these to an image, ending up with a 200 by 200 pixel head shot.

Start with a picture of Lucas

2,048 by 1,536 pixels (shown reduced to fit the slide)

Operation: rotate

1,536 by 2,048 pixels (shown reduced to fit the slide)

Operation: crop

357 by 381 pixel image (shown full size)

Operation: increase contrast

Operation: apply the “ink sketch” filter

This sort of thing took an overnight run in the era of batch processing.

Image processing programs have many such filters.

Operation: resize

50 by 53 pixels

This could be used for an icon on a Web site or in a program.

Operation: resize

200 by 213 pixels

I want to make a 200 by 200 pixel head shot to fit a Web site.

Operation: crop

200 by 200 pixels

15.3 kilobytes40.2 kilobytes

Operation: compress

Tip for Web developers

• Capture images (or audio or video) at the highest resolution possible.

• Do all resizing, cropping, contrast modification, etc. on the high resolution image.

• The last step is compression (if any) and uploading the image to the Web.

Try this for yourself

The original picture of lucas is at:

http://bpastudio.csudh.edu/fac/lpress/netApps/image/lucasoriginal.jpg

A few questions

We illustrated several image processing operations in this presentation. Without looking back, do you recall what they were?

Can you describe what each does to an image?

Can you think of any other image processing operations that we did not use in this presentation?

If one zooms in on an image is information lost or gained?

If one resizes an image, making it smaller, is information lost?

If one resizes an image, making it larger, is information gained?

If one crops an image, is information lost?

If one filters an image, is information lost?

If one compresses an image, is information lost?

If one zooms in on an image, which of its characteristics are changed?

If one resizes an image, which of its characteristics are changed?

If one crops and image, which of its characteristics are changed?

If one filters an image, which of its characteristics are changed?

If one rotates an image, which of its characteristics are changed?

If one compresses an image, which of its characteristics are changed?

An image processing session

Skills: change view (zoom in or out), rotate, select a portion, crop, resize, change contrast, filter, compress

IT concepts: image processing operation

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.