The logarithmic scale emphasizes small histogram values that are not typically noticeable in a linear scale. The use of minor gray-level values becomes more prominent at the expense of the dominant gray-level values. In a logarithmic scale, the vertical axis of the histogram gives the logarithm of the number of pixels per gray-level value. These values might appear unused when the histogram is displayed in a linear scale. A logarithmic scale lets you visualize gray-level values used by small numbers of pixels. The vertical axis of a histogram plot can be shown in a linear or logarithmic scale. The cumulative histogram of the same image shows that the two left-most peaks compose approximately 80% of the image, while the remaining 20% corresponds to the third peak. The linear histogram reveals that the image is composed of three major elements.
The gray-level intervals featuring a concentrated set of pixels reveal the presence of significant components in the image and their respective intensity ranges. The histogram is the function H defined on the grayscale range such that the number of pixels equal to the gray-level value k is Tune your imaging setup until the histogram of your acquired images has the contrast required by your application. In this case, the analysis of the histogram of the image reveals two or more well-separated intensity populations. A strategy to separate the objects from the background relies on a difference in the intensities of both, for example, a bright part and a darker background. Lack of contrast-A widely-used type of imaging application involves inspecting and counting parts of interest in a scene.An overexposed or saturated image contains a large number of pixels with very high gray-level values. This appears as a peak at the lower end of the histogram. An underexposed image contains a large number of pixels with low gray-level values. You can detect whether a sensor is underexposed or saturated by looking at the histogram. It is important to detect these imaging conditions and correct for them during setup of your imaging system. Images acquired under underexposed or saturated conditions will not contain all the information that you want to inspect from the scene being observed. Saturation-Too little light in the imaging environment leads to underexposure of the imaging sensor, while too much light causes overexposure, or saturation, of the imaging sensor.You can detect two important criteria by looking at the histogram. You also can use a histogram to adjust the image acquisition conditions. You can use the histogram to determine whether an image contains distinct regions of certain grayscale values. Use the histogram to determine if the overall intensity in the image is high enough for your inspection task. The histogram is a fundamental image analysis tool that describes the distribution of the pixel intensities in an image. From the graph, you can tell whether the image contains distinct regions of a certain gray-level value.Ī histogram provides a general description of the appearance of an image and helps identify various components such as the background, objects, and noise. A histogram counts and graphs the total number of pixels at each grayscale level.