This option provides access to the dynamic intensity calibration menu. This menu contains options for mapping intensities onto a reference intensity scale, and mapping intensities onto some external field (such as concentration). The basic principle is to include in the field of view some intensity scale with a number of discrete steps. The location of this intensity scale is then registered with DigImage by interactively specifying a number of windows, typically one per step in the intensity scale. DigImage will record the current (reference) intensity in each of these windows, and the value of some external field (such as concentration) associated with each of the intensity steps. Subsequently, DigImage can be asked to determine the current intensity within each of the windows and generate a mapping between the current intensity and the recorded reference level. In addition mappings are generated between the reference intensity and the external field, and between the current intensity and the reference field. Any of these three mappings may be used to modify the intensities of the image. In addition, some features of DigImage (or user written DigImage modules) are able to use these mapping functions directly.
This option allows the intensities of the image in a buffer to be altered by the mapping between the reference intensity levels and the external field. To assist the conversion of the external field back into intensities, values for the external field to be rendered with intensities 0 and 255 are requested.
This option allows the current intensity mapping (as shown by [D Display mappings]) to transform the specified image from its current intensity levels to the reference levels.
This option is similar to [A Apply reference concentration mapping to image] except that the mapping is between the current pixel scale and the external field. Thus (once the mapping has been set up) the intensities may be mapped directly onto the external field. Values for the external field to be rendered with intensities 0 and 255 are also requested.
This option displays the coordinates of the reference windows, their current and reference intensities and the associated external (concentration) field. The three mapping functions are also displayed.
This option requests DigImage to determine the current intensities of the reference windows, and to generate the mapping functions from these current intensities to both the reference intensities and the external field. These mappings do not alter the contents of the buffer, but simply set up the internal mappings. The mappings may be displayed using [D Display mappings] or employed using [B Apply current intensity mapping to image] or [C Apply current concentration mapping to image].
This option is equivalent to [F Find intensity and concentration mappings...] followed by [B Apply current intensity mapping to image]. This is the most convenient method of applying the current to reference intensity mapping to an image.
This option is equivalent to [F Find intensity and concentration mappings...] followed by [C Apply current concentration mapping to image]. This is the most convenient method of converting from the current intensity scale to the associated external field.
This option resets the intensity mapping functions to an identity mapping, and clears all window definitions from DigImage.
This option is used to define the reference windows. The reference intensities are determined automatically (although may be modified using [U Update reference intensities manually]), and the associated external field values are requested. Each call to this option will add further windows to those already defined. Use [I Initialise intensity mapping] to clear any existing windows if desired.
This option is used to specify the function to be used to map between current and reference intensity levels. The mapping procedure employs a least squares fit between the current intensities of the reference windows, and their reference intensities. The function specified is linear in the intially unknown coefficients. The terms in the mapping are specified one at a time.
This option is used to specify the function to be used to map between intensity levels and the associated external field (eg. concentration). The mapping procedure employs a least squares fit between the intensities (current or reference) of the reference windows, and their associated external field value. The function specified is linear in the intially unknown coefficients. The terms in the mapping are specified one at a time.
This option may be used to update the reference intensities to the intensity values of the reference windows in the buffer specified.
This option allows the reference intensity levels associated with the reference windows to be specified manually. These itensities are normally determined during [L Locate intensity reference windows]. Intensities for the reference windows are updated one at a time.
This option allows the values of the external field associated with the reference windows to be altered. These values are normally specified during [L Locate intensity reference windows].
This option is used to specify the transfer function by which the video and frame grabber hardware maps true intensities to intensity values in the frame grabber. Unlike the other mappings in this menu, this hardware transfer function is treated as a static mapping. The quantitative accuracy of the function is less important than its functional form, provided it is applied in a uniform manner to all the images being processed. Normally this mapping would be used to precondition images into an approximately true intensity space in order that basic processing may be undertaken. The dynamic mappings determined by the other options in this menu may then be used to obtain accurate quantitative data.
The transfer function may be applied to an image already acquired by choosing [Y Apply hardware transfer function to buffer], or alternatively the transformation may be applied during acquisition by choosing input look up table 2.
The form of the transfer function should be determined by calibration from a known intensity scale.
This option applies the hardware transfer function, specified by [X Specify hardware transfer function], to the contents of a buffer.