The Histogram / Histogram panel helps you visualize the color balance of an image and visualize color corrections specified with the Korekce barev / Color tool. In addition, it provides powerful tools for loading certain types of color correction values into the Korekce barev / Color tool.

While the Histogram / Histogram panel is active, The Panorama Factory displays a preview rectangle on the current image.

When you place the cursor over the various parts of the preview rectangle it changes to show you what editing actions are possible:

This cursor	Means this
	Indicates that the cursor is over one of the sides or corners of the preview rectangle. Dragging changes the size of the rectangle.
	Indicates that the cursor is not over any part of the preview rectangle. Dragging draws a new preview rectangle.

The Panorama Factory displays three types of information on the Histogram / Histogram panel and updates them as you change the color correction values:

The histogram of color values within the preview rectangle are shown with a line graph. Separate lines are displayed for the red, blue and green components of the image.

The transfer function specified by the color correction tool. Separate lines are displayed for the red, blue and green components of the transfer function.

The average red, green and blue values within the preview rectangle are shown as triangles at the top of the graph. This shows you the average color cast within the preview rectangle. For example, if the average is a shade of gray, the three triangles are superimposed.

You can also select one or more thumbnail images to show the histogram of the thumbnails. Note that this computes the histogram of the sub-sampled thumbnail images. This histogram may differ slightly from the histogram of the full resolution images they represent.

The Histogram / Histogram panel offers the following controls:

Bez úprav / Uncorrected
Select this radio button to show the histogram of the image prior to color correction.

Upravit / Corrected
Select this radio button to show the histogram of the image after applying color correction.

Nastavit černou / Set black
Simultaneously sets the level, color and balance of the black point according to the average value within the preview rectangle. This provides a convenient way of setting the black point for negative images. Draw the preview rectangle within an inter-frame region of the negative and then press this button.

Nastavit šedou / Set gray
Sets the midrange color and balance, but not level, to make the average value within the preview rectangle be a shade of gray. This provides a convenient way of correcting the color balance of the image if it contains a gray reference. Draw the preview rectangle within the gray reference and then press this button. An 18% gray card provides a good gray reference, but you can also use any whitish object in the image as long as its brightness is not too near the white or black point. It is best to use the tool only after setting the white and black points.

Nastavit bílou / Set white
Simultaneously sets the level, color and balance of the white point according to the average value within the preview rectangle. This provides a convenient way of setting the white point for positive images printed on white paper with a border. Draw the preview rectangle within the border region and then press this button.

Left mouse button
Clicking or dragging the left mouse button within the histogram graph moves the black level to the mouse position.

Right mouse button
Clicking or dragging the right mouse button within the histogram graph moves the white level to the mouse position.