Pixel Reading - knowing the gray level of a specific pixel

The pixel reading allows us to know the gray level of a specific pixel and that of its neighbors. This function does not produce nor allows any changes on the original image.

Such analysis is useful for works that involve the study of spectral response of targets, in various bands of multispectral images.

SPRING presents the digital levels of the pixels of the visualized bands. The values shown correspond to the pixels that are present on the original image, independently from the image visualization scale on the screen.

The pixel reading (gray levels or colored composite) can be performed in two ways: either click in a point on the image or place the cursor in a point of geographic, planes or line/columns coordinates.

Reading the gray levels of an image:

  • select an image on the "Control Panel" in Monochromatic or RGB composition;
  • click on Execute - Draw( atalho_desenhar.gif - 941 Bytes) on the main menu;
  • click on image - Pixel Value... on the main menu;
  • click on View - Cross - Cursor ( atalho_curso_pto.gif - 940 Bytes) on the main menu. By default this cursor become active when you opened the window "Pixel Value" for the first time;
  • click on an image and you will see a green cross over it. To cancel the cross cursor, click again on View - Cross - Cursor. Notice that every time you click on the image, the gray levels (GL) will be presented on the window.

NOTE: Besides the Gray Levels, the geographic, planes and image coordinates of the chosen point will also be presented on the window.

Reading Pixels:

  • click on Image - Pixel Values... on the main menu after having the image presented on the drawing area;
  • click on Set Cursor Position... or in Tools - Set Cross-Cursor Position...;
  • the Gray Levels are presented each time you press Apply on the "Set Cursor Position" window.

Saving the data presented on the Image - Pixel Values... window:

  • click on Save...;
  • a SPRING window is presented and you should type in a name for a text file (txt) to save the data.

The list with values is cumulative. So, if you want to clean it see the instructions below:

Removing values:

  • on the window "Pixel Values" click on Delete to remove the undesired data.

See also:

Read more about Image Processing Techniques
Image Processing Menu