X-Git-Url: http://gitweb.fperrin.net/?p=GpsPrune.git;a=blobdiff_plain;f=src%2Ftim%2Fprune%2Fgui%2Fmap%2FMapUtils.java;fp=src%2Ftim%2Fprune%2Fgui%2Fmap%2FMapUtils.java;h=49d94676f77c70cc137fa1d204a11dffcd4eea27;hp=0000000000000000000000000000000000000000;hb=ce6f2161b8596f7018d6a76bff79bc9e571f35fd;hpb=2d8cb72e84d5cc1089ce77baf1e34ea3ea2f8465

diff --git a/src/tim/prune/gui/map/MapUtils.java b/src/tim/prune/gui/map/MapUtils.java
new file mode 100644
index 0000000..49d9467
--- /dev/null
+++ b/src/tim/prune/gui/map/MapUtils.java
@@ -0,0 +1,101 @@
+package tim.prune.gui.map;
+
+import java.awt.Color;
+import java.awt.image.BufferedImage;
+
+/**
+ * Class to manage coordinate conversions and other stuff for maps
+ */
+public abstract class MapUtils
+{
+	/**
+	 * Transform a longitude into an x coordinate
+	 * @param inLon longitude in degrees
+	 * @return scaled X value from 0 to 1
+	 */
+	public static double getXFromLongitude(double inLon)
+	{
+		return (inLon + 180.0) / 360.0;
+	}
+
+	/**
+	 * Transform a latitude into a y coordinate
+	 * @param inLat latitude in degrees
+	 * @return scaled Y value from 0 to 1
+	 */
+	public static double getYFromLatitude(double inLat)
+	{
+		return (1 - Math.log(Math.tan(inLat * Math.PI / 180) + 1 / Math.cos(inLat * Math.PI / 180)) / Math.PI) / 2;
+	}
+
+	/**
+	 * Transform an x coordinate into a longitude
+	 * @param inX scaled X value from 0(-180deg) to 1(+180deg)
+	 * @return longitude in degrees
+	 */
+	public static double getLongitudeFromX(double inX)
+	{
+		// Ensure x is really between 0 and 1 (to wrap longitudes)
+		double x = ((inX % 1.0) + 1.0) % 1.0;
+		// Note: First %1.0 restricts range to (-1,1), then +1.0 shifts to (0,2)
+		// Finally, %1.0 to give (0,1)
+		return x * 360.0 - 180.0;
+	}
+
+	/**
+	 * Transform a y coordinate into a latitude
+	 * @param inY scaled Y value from 0 to 1
+	 * @return latitude in degrees
+	 */
+	public static double getLatitudeFromY(double inY)
+	{
+		double n = Math.PI * (1 - 2 * inY);
+		return 180 / Math.PI * Math.atan(0.5 * (Math.exp(n) - Math.exp(-n)));
+	}
+
+	/**
+	 * Tests whether there are any dark pixels in the image within the specified x,y rectangle
+	 * @param inImage image to test
+	 * @param inX left X coordinate
+	 * @param inY bottom Y coordinate
+	 * @param inWidth width of rectangle
+	 * @param inHeight height of rectangle
+	 * @param inTextColour colour of text
+	 * @return true if the rectangle overlaps stuff too close to the given colour
+	 */
+	public static boolean overlapsPoints(BufferedImage inImage, int inX, int inY,
+		int inWidth, int inHeight, Color inTextColour)
+	{
+		// each of the colour channels must be further away than this to count as empty
+		final int BRIGHTNESS_LIMIT = 80;
+		final int textRGB = inTextColour.getRGB();
+		final int textLow = textRGB & 255;
+		final int textMid = (textRGB >> 8) & 255;
+		final int textHigh = (textRGB >> 16) & 255;
+		try
+		{
+			// loop over x coordinate of rectangle
+			for (int x=0; x<inWidth; x++)
+			{
+				// loop over y coordinate of rectangle
+				for (int y=0; y<inHeight; y++)
+				{
+					int pixelColor = inImage.getRGB(inX + x, inY - y);
+					// split into four components rgba
+					int pixLow = pixelColor & 255;
+					int pixMid = (pixelColor >> 8) & 255;
+					int pixHigh = (pixelColor >> 16) & 255;
+					//int fourthBit = (pixelColor >> 24) & 255; // alpha ignored
+					// If colours are too close in any channel then it's an overlap
+					if (Math.abs(pixLow-textLow) < BRIGHTNESS_LIMIT ||
+						Math.abs(pixMid-textMid) < BRIGHTNESS_LIMIT ||
+						Math.abs(pixHigh-textHigh) < BRIGHTNESS_LIMIT) {return true;}
+				}
+			}
+		}
+		catch (NullPointerException e) {
+			// ignore null pointers, just return false
+		}
+		return false;
+	}
+}