Combining images with drawings in maps can lead to spectacular presentation graphics. Image effects allow a wide range of graphics arts effects when combined with drawings. This topic creates a presentation map using editing in drawings, drop shadows created with Gaussian blur, and a color gradient applied to an image.
Step 1: Prepare drawing
Import US_Main and create a drawing using the procedures given in the Create a Projected US Map topic.
Open the drawing in a drawing window. We will use Smart Mouse Selection and drawing editing to move states around. Make sure the mouse is not occupied with a command mode (such as Zoom or some other mode) and click on the state of Washington.
The state becomes selected as the primary selected object, ready for editing, with edit handles appearing. Edit handles overlap densely at the zoom level illustrated. Click on any of the edit handles and drag to the upper left.
Clicking and dragging an edit handle moves the entire object to the upper left.
Release the click and drag and the state of Washington snaps to its new location.
Click on the state of Oregon to select it for editing and then click on any edit handle and drag it to the left.
Release the click and drag and Oregon will move to its new location.
Continue in this way to move western states away from the main part of the drawing. Save the project as a .map. It is always wise to save work in a project against the chance of irreversible user errors.
Step 2: Create a Drop Shadow
We will now create a "drop shadow" for this rendering of the United States. A drop shadow is a graphics layer that gives the appearance of a shadow, as if the item above it were physically suspended above the page and casting a shadow. To create a drop shadow we begin by saving the drawing as an image.
Choose Tools - Make Image command, saving the image using the name "Shadow Mask." We've picked a name that sound a bit strange for now, but it will make sense later.
The default size of the image will be that seen for the drawing at display monitor resolution. Choosing the image size at this stage of our procedure will affect the quality (resolution) of the drop shadow. If the map we are creating will be printed out on a large scale we may wish to use a much higher resolution image. To do so we could first create a print layout for the drawing and then use the Make Image command for the layout (when used with layouts the Make Image command allows specification of image resolution).
The result is an image called Shadow Mask. We open this image in an image window and see it is image that is 1200 by 900 pixels in size that is a raster image rendering of the drawing we had created. It appears with blurry border lines in the illustration above because the view is zoomed out to enable the image to be seen at reasonable size in this topic.
We have zoomed out far enough so the extent of the image is clear. Beyond the edge of the image we see the default, "transparent" background. Note that when Manifold created the image from the drawing it used the background color, white, to fill in the "empty" white space around the area objects.
We will use this image to create a drop shadow. However, because the blue regions from the area objects press right up to the edges of the image we first need to add margin to the image to provide a larger image into which the Gaussian blur can reach.
We add margin using the Transform toolbar and the Add Margin operator. As see above, we will add 100 pixels to the margin.
The result is a 100 pixel margin added in black color. To make the black margin match the rest of the image we will use the Paint Bucket tool to fill it with white color.
Click on the foreground color in the format toolbar for images and make it white (the illustration shows both foreground and background color wells in white color).
Click on the paint bucket tool and then click anywhere in the black margin.
The paint bucket tool will fill the region of contiguous black pixels with white color.
Our next task is to make all pixels in the blue map region black in color. We need to select all pixels that are not white.
The easiest way to do this is with Select Touch and SHIFT clicking onto any of the white pixels. This selects all of the white pixels in the image. We use SHIFT to extend the touch selection to all white pixels and not just those that are contiguous to the pixel on which we clicked. Had we not used SHIFT there might have been some white pixels in the Great Lakes or the upper parts of Chesapeake Bay or other enclosed regions that would not have been selected.
To select all non-white pixels we simply choose Edit - Select Inverse to invert the selection. It would have been difficult to select all non-white pixels using touch selection because they are a mixture of blue and gray colors. In this case it was much easier to select the white pixels and the invert the selection.
We launch Hue / Saturation and move the Lightness slider all the way to the left to force all of the selected pixels to black. Press OK.
The result (seen after pressing Select None so there is no selection) is that all of the non-white pixels have been converted to black color.
We can now create a Gaussian blur shadow by choosing Gaussian Blur . The number of pixels used for the blur depends upon the shadow effect desired and the resolution (size of the image in pixels) of the image. Using larger numbers of pixels results in larger "shadows." Large and faint shadows can provide a visual cue that the object is "floating" farther away from its background. Smaller and dark shadows indicate the object is closer to its background.
Beginners might want to experiment with Preview checked to see the effect obtained.
The result is a blurred image of the black pixel regions. The astute reader may have already thought ahead to how this might be used as a layer under a vector drawing layer to create the impression of a shadow.
Step 3: Create a map using a shadow image
To use a shadow image under a drawing layer we need to work with a map, because only maps in Manifold have layer structure as we would like to use. We use the US_Main drawing to create a map. We then open the map. Because we will need the Shadow Mask image for other purposes, we will first Copy the Shadow Mask image in the project pane and Paste to create a second image that we call Shadow.
We drag and drop the Shadow image into the map, right click on the Shadow tab and choose Order to move it below the US_Main layer. The illustration above shows the tab separately from the illustration of the map to provide a more compact illustration. Note that the image is correctly georegistered to the drawing. It was originally created from the drawing and so continues to be georegistered to the drawing. However, the blur effect is not what we would like. To create a drop shadow effect the image should be displaced from the drawing.
To offset the drawing from the shadow we click on the US_Main layer to make it active.
Using the Grabber tool, we do a CTRL-click-and-drag slightly to the upper left. This moves the drawing relative to the drop shadow. We could have clicked on the Shadow layer and used CTRL-click and drag slightly down and to the right to move the shadow instead of moving the drawing. The visual effect obtained would be the same. Note: moving layers with a CTRL-grabber works only if the layer and the map both use the same projections, differing only in local offset or local scales.
At this point, the drop shadow effect is achieved for many purposes. If desired, we can right click on the Shadow layer and choose Opacity to alter the opacity of the shadow layer. Altering the opacity of a layer bearing a drop shadow will alter the lightness of the shadow and can provide a more realistic effect.
However, there is a problem with the map we have constructed that unchecking the Background box in the Layers pane reveals. With the background turned off we can see all layers against the checkerboard default background. In particular, we can see that the Shadow image has a large region of white pixels. The shadow is constructed in that image by blending black pixels in a Gaussian blur into a field of white pixels. That's fine for an effect if we desire a white background and if the Shadow layer is to be the lowest layer in our map.
Step 4: Create a drop shadow using alpha transparency
Suppose, though, we would like another drawing layer to appear below the US_Main layer and its shadow, so that the United States appear to float above another drawing and to cast a shadow on that layer? In that case, the shadow layer must be constructed so that the black shadow blurs or "feathers" into transparency, not into white pixels. This is an effect that can be achieved using a short sequence of sophisticated steps.
First, we open the Shadow Mask image in its own window. We then use Image - Convert To to convert it into a Grayscale image. We then close the Shadow Mask image.
Next, we open the Shadow image in its own window. We use Image - Convert To to convert it into an RGBa image.
With the focus on the Shadow image window, we launch Hue / Saturation and move the Lightness slider all the way to the left to force all of the pixels in the image to black. We leave this image window open because we have one more command to apply to the image.
We can see the effect of forcing all of the pixels in the Shadow image to black. It seems very counterproductive since it destroys the shadow effect.
With the focus on the Shadow image window we choose Edit - Load Mask/Channel .
In the Load Mask/Channel dialog we load the alpha channel using the Shadow Mask image. This is why we named it "shadow mask" when it was created and why we converted it to a grayscale image. Only grayscale images can be used as masks. Because we created the Shadow image from the Shadow Mask image both are exactly the same size and thus the Shadow Mask can be used as a mask. Remember that the Shadow Mask image shows a Gaussian blur drop shadow in shades from black to white. If we use this as a mask for the alpha (transparency) channel of an RGBa image we will be superimposing a transparency gradient upon the Shadow image that follows exactly the pattern of the Gaussian blur in the Shadow Mask image. Applying such a transparency gradient to the all black Shadow image will result in a gradient from solid black pixels to fully transparent pixels with partial transparency in the region of the Gaussian blur effect. We will have achieved a blur from black into transparency.
The moment we press OK in the Load Mask / Channel dialog we can see the effect in the map window. There is no longer any solid appearance to the Shadow layer in any location other than the actual shadow. We can now create layers under the Shadow layer and they will show through as desired.
Step 5: Add a graticule
To show the effect of the transparent drop shadow we can add a graticule underneath the US_Main and Shadow layers.
Right click the US_Main layer tab in the drawing and choose Add - Drawing to add a drawing. Name it Graticule.
In the Tools - Options - Colors dialog change the graticule color to black.
Choose View - Graticule to launch the Graticule dialog. Use the settings shown above and push Create to create a graticule as line objects in the Graticule drawing layer.
The result is a graticule grid that appears in the layer. We can right click on the layer tab and choose Order to move the layer tab to the bottom of the layer stack.
To achieve a lighter shadow effect, we right click on the Shadow layer and choose Opacity. In the Opacity dialog we set the transparency of the layer to 50 percent and press OK.
The result is a map using a transparent drop shadow that allows layers beneath it to show through. Note how the partially transparent shadow produces a natural effect where it overlays the graticule lines.
Step 6: Add a gradient color effect
A combination of images and drawings in maps can create many effects in addition to drop shadows. For example, we can color the US using a gradient of color. [This example shows a purely artistic effect. If we want to show data as gradients we could use surfaces.]
To create the effect desired we need to create another image from US_main. We do this by opening the US_Main drawing in its own drawing window and then choosing Tools - Make Image as we did before.
We will create an image called Gradient.
If we click open the Gradient image in its own window we can see that it is similar to the Shadow Mask image we created to use in building a drop shadow.
Using the Select Touch tool we SHIFT-click on the white pixels to select all white pixels.
Press Delete to delete the white pixels. We now need to select the other pixels. To do this, we SHIFT-click onto the region of invisible pixels and then choose Edit - Select Inverse to invert the selection. The result is to select all of the remaining, visible pixels.
To create a color gradient we choose the colors in the format toolbar foreground and background colors that will define the gradient.
Select the gradient tool .
Create a gradient by clicking on the left side of the image with the gradient tool and then dragging to the right side and releasing. The color gradient will be created along this line within the selected pixels.
Instantly, we achieve a dramatic coloring effect in the Gradient image.
If we drag and drop the Gradient image into our map as the uppermost layer we see the dramatic effect in the map as well. Because the Gradient image was created from the US_Main drawing it is georegistered to that drawing and overlays it perfectly.
We may want to show borders for states in the composite map. To do this we must create a drawing layer of state boundaries above the Gradient layer.
Click on the US_Main layer and run the transform toolbar using the Boundaries operator.
This creates line objects in the US_Main layer that outline the boundaries of the state areas. We can cut these out of the drawing using CTRL-X or Edit - Cut. We can then right click onto the Gradient layer and choose Add - Drawing to create a new drawing. We can then paste the boundaries into the new layer with CTRL-V or Edit - Paste.
The final result is a dramatic map that was created using a mixture of image and drawing techniques.
Comments
The images used in this procedure are slightly larger than necessary because the initial size of 1200 x 800 used in the Make Image dialog results in unnecessarily large borders around parts of the image. We could have reduced the size of the images by using Crop after creating the Gaussian blur.
It is usually better to create a drop shadow effect by repositioning the layer containing the drop shadow than it is to move the objects being shadowed as was done in this example.
The map shown uses a gradient image at the end to color the states of the US. If desired, this step could be skipped and the "blue" drawing thematically formatted. Moving the states to new positions for artistic effect does not change their status as objects: they can still be thematically formatted to show trends in population or other variables.
The planned use of the map should be considered when specifying the size of the drop shadow created using Gaussian blur. A blur of 30 pixels as used in this example works well when a large image is seen in a zoomed out view as a small portion of the monitor. Using a blur much smaller than that would result in a too-thin shadow. However, when zooming into the view or printing on a larger sheet of paper 30 pixels of blur may prove too much. Experience will reduce the need for trial and error.
While gaining experience, make a copy of the black and white image and then apply Gaussian blur to the copy. One can then relatively easily fall back and use a different level of blur if the original effect proves disappointing. Changing the perceived blur in the shadow used in the map is easy, since once we create a new Gaussian blur mask we simply re-load the alpha channel with the new mask.