A histogram is a graphical way of representing statistics related to image brightness. A one dimensional histogram, like the ones shown here, depict the amount of image area (vertical axis) that corresponds to particular brightness values (horizontal axis). Analysis of the histogram of an image allows the interpreter to objectively identify the pixel population of the image as classified into brightness levels.
How well do you know your histograms? Match the histogram to each image.
Hint for Image 1: Notice that most of the image is bright, with a small amount of mid-grey and very dark areas.
Hint for Image 2: There appears to be a full range of greys in this image.
Hint for Image 3: There are two distinct shades of mid-grey in this image, each represented by the two large fields. The light-toned road in the bottom of the image has a small relative area and a narrow range of grey levels.
Hint for Image 4: The grey levels in this image are all mid-level, with a complete absence of lighter shades.
Hint for Image 5: More than half of the area in this image has a narrow range of dark tones representing the water. The land contains a wide range of mid to high tones.
Hint for Image 6: Most of the area of this image is taken with a wide range of mid to high tones representing the land. On the water side, a small fraction of the image is covered with a narrow range of dark tones.
Hint for Image 7: Most of the area of this image is taken with a wide range of mid to high tones representing the land. On the water side, a small fraction of the image is covered with a narrow range of mid-grey tones.
Did You Know?
A histogram or "frequency distribution" of an image allows the analyst to:
- detect some possible problems in the processing of a digital image,
- plan appropriate enhancements for the visual interpretation of an image,
- plan suitable classification schemes for an image or image portion,
- plan suitable ground truthing in support of image classification,
- prepare for appropriate mosaicking methods of several images,
- and more!
single band images
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