Access the display options from the control center using the Layer Options toolbar button, or right clicking on the layer name and selecting Options. It will also open when double-clicking on the layer name. The Raster Options and Elevation options dialogs contain a display tab.
The Color Intensity setting controls whether displayed pixels are lightened or darkened before being displayed. It may be useful to lighten or darken raster overlays in order to see overlaying vector data clearly.
The Translucency setting controls to what degree the overlay displays the overlays underneath it. Settings closer to Transparent make the overlay increasingly more see-through, allowing you to blend overlapping data.
With palette files, the available colors will be automatically populated in the list on the left. Select multiple transparent colors using the CTRL or SHIFT key and clicking the palette colors. CTRL can also be used with the Pick from Map tool to pick multiple colors in a palette file.
With other raster files, the Transparent color list will be empty to begin with. Use the Pick from Map or Pick From Table buttons to add colors to the list. Highlighted colors will be set at transparent. Use the SHIFT or CTRL keys to highlight multiple transparent colors once picked.
Pick from Table - This option is available for imagery or elevation layers that do not contain a palette. This will display the Color selection dialog. Select a basic color, or use the settings on the right to fine tune the color by Hue, Saturation and Luminosity, or Red Green and Blue values.
Add to Custom Colors – This adds the color to the list of custom colors, shown below the basic colors.
Pick Color From Map – when this option is selected the cursor will change to an eyedropper. Click on any 2D map to select the color value at the cursor location.
Save to File – This will save the list of colors to a palette file.
The Exact to Fuzzy slider in the Transparency section controls how similar to the selected transparent color(s) that a color in the image has to be before it is also treated as transparent. The Exact side means that only exact matches on color will be treated as transparent, moving the slider towards the Fuzzy side makes progressively less similar colors be treated as transparent. This is useful for getting rid of colors in lossy formats like JPG and ECW where the colors are not exact.
To remove listed transparent colors, click Set Transparent Color and select a color from the list, then click the Delete key. To delete multiple colors at once, hold the ALT key and select multiple listed colors, then click the Delete key. To delete all colors, hold the SHIFT key and select the top most listed color and then select the bottom listed color, then click the Delete key.
Online Layer Detail Offset
The Online Layer Detail Offset allows for online layers to draw data at a lower resolution for faster display. The detail control of online layers will enable pulling data from lower or higher resolution layers, rather than the default screen resolution calculation.
The Blend Mode setting controls
how an overlay is blended with underlying overlays, in addition to the
Translucency setting. These settings allow Photoshop-style filters to
be applied to overlays. The results from a particular blend mode with
different sets of overlays can often be difficult to predict. It is best
to experiment with different settings. The Hard
Light setting works well with satellite imagery overlaid on DEMs,
but the others can be quite useful as well.
as using a low-resolution color LANDSAT image to colorize a high-resolution grayscale satellite image. The SPOT Natural Color blend mode combines the color channels in the topmost layer using the common algorithm for generating natural color imagery from images from the SPOT HRV multi-spectral sensor [Red = B2; Green = ( 3 * B1 + B3 ) / 4; Blue = ( 3 * B1 - B3 ) / 4]. The Pseudo Natural Color blend mode combines the color channels within a single image using a common algorithm for generating natural color imagery from CIR imagery. The Color to Grayscale blend mode converts a color image to grayscale.
- Nearest Neighbor - simply uses the value of the sample/pixel that a sample location is in. When resampling an image this can result in a stair-step effect, but will maintain exactly the original color values of the source image.
- Bilinear Interpolation - determines the value of a new pixel based on a weighted average of the 4 pixels in the nearest 2 x 2 neighborhood of the pixel in the original image. The averaging has an anti-aliasing effect and therefore produces relatively smooth edges with less stair-step effect.
- Bicubic Interpolation - a more sophisticated method that produces smoother edges than bilinear interpolation. Here, a new pixel is a bicubic function using 16 pixels in the nearest 4 x 4 neighborhood of the pixel in the original image. This is the method most commonly used by image editing software, printer drivers, and many digital cameras for resampling images.
- Box Average (3x3, 4x4, 5x5, and 7x7) - the box average methods simply find the average values of the nearest 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), or 49 (for 7x7) pixels and use that as the value of the sample location. These methods are very good for resampling data at lower resolutions. The lower the resolution of your export is as compared to the original, the larger "box" size you should use.
- Filter/Noise/Median (2x2, 3x3, 4x4, 5x5, 6x6 and 7x7) - the Filter/Noise/Median methods simply find the median values of the nearest 4 (for 2x2), 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), 36 (for 6x6) or 49 (for 7x7) pixels and use that as the value of the sample location. This resampling function is useful for noisy rasters, so outlier pixels do not contribute to the kernel value. Some common sources of raster noise are previous compression artifacts or irregularities of a scanned map/image.
- Box Maximum (3x3, 4x4, and 5x5) - the box maximum methods simply find the maximum value of the nearest 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), or 49 (for 7x7) pixels and use that as the value of the sample location. These methods are very good for resampling elevation data at lower resolutions so that the new terrain surface has the maximum elevation value rather than the average (good for terrain avoidance). This method behaves the same as the average on raster/imagery layers. The lower the resolution of the export file is as compared to the original, the larger "box" size that should be used.
Map option allows a 2D raster overlay to be draped over loaded
3D elevation overlays. Selecting the check box causes the overlay to use
any available data from underlying elevation layers to determine how to
color the DRG or DOQ. The result is a shaded relief map.