Image General Properties
Image files can be loaded into Surfer with the Home | Insert | Graphic command. Click on the Image object in the Contents window to open the image properties in the Properties window. If you wish to use the image in a base (raster) layer, and georeference the image, use the Home | New Map | Base or Home | Add to Map | Layer | Base command instead.
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The General page controls the image appearance and shows the Spatial Extents. |
Image Properties
The first five properties on the General page transform the image appearance: Opacity, Contrast, Brightness, Saturation, and Hue. These image transformations are applied to the display of the image or base layer, not to the image file. However, the image transformations are saved to the exported file when exporting the image or map.
Opacity
Change the Opacity of an image by entering a value from 0% (completely transparent) to 100% (completely opaque) or dragging the 
to change the opacity percentage.
Contrast
Contrast is the difference in luminance or color of the objects in the image. Light and dark objects appear to stand out from one another when contrast is high. The difference in luminance between objects is difficult to see when contrast is low. The Contrast value is relative in Surfer. The original image is given a Contrast value of 0. Positive values increase the image contrast. Negative values decrease the image contrast. Type a value between -100 and 100 in the Contrast field or click and drag the to adjust the image contrast.
Brightness
Brightness is the perception of emitted or reflected light. Brightness can also be considered the average of the Red, Green, and Blue values for the pixels in the image. As brightness increases objects become lighter until they begin to "wash out" or turn white. Objects in the image get darker until they become black as brightness decreases. The Brightness value is relative in Surfer. The original image is given a Brightness value of 0. Positive values increase the image brightness. Negative values decrease the image brightness. Type a value between -100 and 100 in the Brightness field or click and drag the to adjust the image brightness.
Saturation
Saturation is a combination of light intensity and distribution across different wavelengths. High saturation relates to vivid, bright colors, i.e. high intensity across a narrow wavelength band or even single wavelength. This can also be considered very pure color. Low saturation leads to muted or gray colors, i.e. low intensity across a wide band of wavelengths. No saturation transforms the image to grayscale. The Saturation value is relative in Surfer. The original image is given a Saturation value of 0. Positive values increase the image saturation. Negative values decrease the image saturation. Type a value between -100 and 100 in the Saturation field or click and drag the to adjust the image saturation.
Hue
Hue describes the colors in the image. The Hue property shifts the colors in the image around the color wheel. The Hue value is relative in Surfer. The original image is given a Hue value of 0. Positive values shift the colors in the red to orange, then yellow, green, blue and finally magenta direction. Negative values shift colors in the opposite direction, from red to magenta then blue, green, yellow and finally orange. Type a value between -180 and 180 in the Hue field or click and drag the to adjust the image hue.
Reset
Click Reset to return the image to its original appearance. This sets Opacity to 100% and Contrast, Brightness, Saturation, and Hue to 0.
Transparency
The Transparency section includes properties for defining a color to make transparent in the image.
Use Alpha Channel
Select Use alpha channel to use the fourth channel of data as alpha for transparency. This setting is independent of Set transparent color and Opacity on the Layer page.
Set Transparent Color
Select Set transparent color to specify a color to make transparent in the image. This can be useful when the image includes a background or some other solid color element you wish to remove from the display.
Transparent Color
Specify the color to make transparent in the Transparent color field. Select a color from the color palette or click 
to set a custom color in the Colors dialog.
Tolerance
Specify a tolerance to include colors near the Transparent color to also make transparent. Select a tolerance between 0 - 255. A Tolerance of 0 means the color in the image must match the Transparent color exactly. As Tolerance increases, more colors are included.
Click Reset to return the image to its original appearance. This sets Opacity to 100% and Contrast, Brightness, Saturation, and Hue to 0.
Spatial Extents
The Left, Right, Bottom, and Top values in the Spatial Extents group displays the current extents of the image. These values are read-only. Click the Georefence image button to change the spatial extents.
Georeference
When an image is included in a base (vector) layer, the Georeference property is available. Click Georeference image in the Georeference field to apply control points to the image and reference it to your map's coordinate system. Clicking Georeference image opens the Georeference Image window. The image must be at least 2x2 pixels to be georeferenced.
The Georeference Image command is only available in the image properties when the image is part of a base (vector) layer. An image is only part of a base (vector) layer when the base map was created from a file format that includes both vector and raster data. A base (raster) layer is created when creating a base map from an image file, and the image properties are found in the General page for the base (raster) layer.