Histogram
lastmod 2024-03-05created 2016-02-264 edits
A histogram is a graphical representation of a frequency distribution given in a table. Put more simply, it is a frequency distribution table drawn as a graph. In a histogram, the horizontal axis usually represents the classes and the vertical axis the frequencies, though it is sometimes drawn the other way around. The classes are usually intervals of a variable and do not overlap. In the figure, the classes (bars) must touch each other. A histogram differs from an ordinary bar graph. A bar graph shows values only by vertical height without considering the classes, i.e. the width, whereas a histogram must consider both width and height together.
In industry, the histogram is also one of the seven tools of quality control (QC). These are the histogram, Pareto chart, check sheet, control chart, cause-and-effect diagram, flowchart, and scatter diagram. For details, see quality control.
About Histogram
A histogram shows the overall brightness distribution and saturation (how light or dark the colors are) of an image.
Cambridgeincolor_in_Color.jpg
In the lower graph of the figure above, the X axis is the color intensity (0 ~ 255) and the Y axis is the number of colors at each X value. From the graph alone, you can tell that the image's brightness distribution has almost no midtones and many dark and bright colors. Looking at the actual original image, it matches the result of analyzing the graph alone.
See also
- OpenCV
- Histogram specification or Histogram matching
- cv2.calcHist
- np.histogram