Scatter plot of intensities for two images

This option produces a scatter plot showing how the intensities on two images are related on a point by point basis. For each pixel, the intensities on one image are used as the horizontal coordinate, and the other axis the vertical coordinate.

First source buffer (intensities used for x axis) ?

This entry specifies the buffer from which the horizontal axis data is gained. Any DigImage buffer may be specified.

Second source buffer (intensities used for y axis) ?

This entry specifies the buffer from which the vertical axis data is gained. Any DigImage buffer may be specified. This may be the same buffer as for the x axis data.

Scatter plot using Window or whole Screen ?

The plot may be generated from data in the entire buffer (<S>), or a subwindow (<W>).

{If window selected}

Window Selection: Region for Scatter Plot

If the plot is to be made for a window, then the DigImage Window Selection submenu will be produced to enable window specification. For help on the selection process, consult the [H Help] option within the submenu.

Shift second buffer by what vertical displacement ?

The second buffer may have a translation imposed on it prior to the generation of the scatter plot. If i,j are the pixel coordinates, and di,dj the imposed translation, then pixel i,j on the first buffer will be assume to correspond to pixel i+di,j+dj on the second. Wrapping occurs at the limits of the buffer. The vertical displacement is positive DOWNWARDS.

Shift second buffer by what horizontal displacement ?

This entry specifies the horizontal displacement applied to the second buffer. Refer to previous item for further details.

Place scatter plot in which buffer ?

This entry specifies the buffer in which the scatter plot is produced. The buffer will be made the current output buffer, and the plot will be visible during its formation. The intensity of each pixel block is equal to the number of pixels having the corresponding intensities in the two buffers (ie. we are effectively plotting the joint probability function).

Erase scatter plot buffer first ?

Answering yes (<Y>) will erase the buffer on which the plot is produced prior to its creation. No (<N>) allows a series of images to be compared and plotted on the same plot.

Correlation coefficient: !!R0:=!!GR0

The correlation coefficient for the images is returned in the !!R0 variable.

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DigImage User Documentation

Stuart Dalziel, last page update: 19 February 1996