dtedcachehandler.java

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            if (Debug.debugging("dteddetail")) {
                Debug.output("DTEDCacheHandler: frameCacheSize remains at: "
                        + numFramesNeeded);
            }
        } else {
            // calculate how many frames should be in the cache...
            numFramesNeeded = (int) (Math.abs(frameUp - frameDown)
                    * Math.abs(frameRight - frameLeft) * 2);
        }

        if (xPixInterval != xpi || yPixInterval != ypi) {

            // Screen attributes changed!!!!
            xPixInterval = xpi;
            yPixInterval = ypi;

            // While it changed...
            dfsi.xPixInterval = xPixInterval;
            dfsi.yPixInterval = yPixInterval;

            // Trap for funky values...
            if (xpi == 0 || ypi == 0) {
                numXSubframes = 0;
                numYSubframes = 0;
                return;
            }

            int frame_width = (int) Math.ceil(1.0 / xpi);
            int frame_height = (int) Math.ceil(1.0 / ypi);

            // Even number of subframes in frame
            numXSubframes = frame_width / SF_PIXEL_HW;
            lastSubframeWidth = SF_PIXEL_HW;
            numYSubframes = frame_height / SF_PIXEL_HW;
            lastSubframeHeight = SF_PIXEL_HW;

            if (frame_width % SF_PIXEL_HW != 0) {
                lastSubframeWidth = frame_width - (numXSubframes * SF_PIXEL_HW);
                numXSubframes++;
            }
            if (frame_height % SF_PIXEL_HW != 0) {
                lastSubframeHeight = frame_height
                        - (numYSubframes * SF_PIXEL_HW);
                numYSubframes++;
            }

            currentFrameCacheSize = numFramesNeeded;

            frameCache.resizeCache(numFramesNeeded,
                    numXSubframes,
                    numYSubframes);
            if (Debug.debugging("dteddetail")) {
                Debug.output("DTEDCacheHandler: frameCacheSize set to: "
                        + numFramesNeeded);
            }

            if (Debug.debugging("dted"))
                Debug.output("***** Screen Parameters Changed! \n"
                        + " Frame width (pix) = " + frame_width + "\n"
                        + " Frame height (pix) = " + frame_height + "\n"
                        + " Num x subframes = " + numXSubframes + "\n"
                        + " Num y subframes = " + numYSubframes + "\n"
                        + " last sf width = " + lastSubframeWidth + "\n"
                        + " last sf height = " + lastSubframeHeight + "\n"
                        + " X pix interval = " + xpi + "\n"
                        + " Y pix interval = " + ypi + "\n");

        } else if (Math.abs(numFramesNeeded - currentFrameCacheSize) > numFramesNeeded / 2) {
            currentFrameCacheSize = numFramesNeeded;
            frameCache.resizeCache(numFramesNeeded);
            if (Debug.debugging("dteddetail")) {
                Debug.output("DTEDCacheHandler: frameCacheSize set to: "
                        + numFramesNeeded);
            }
        }
    }

    /**
     * Returns the next OMRaster image. When setProjection() is
     * called, the cache sets the projection parameters it needs, and
     * also resets this popping mechanism. When this mechanism is
     * reset, you can keep calling this method to get another subframe
     * image. When it returns a null value, it is done. It will
     * automatically skip over window frames it doesn't have, and
     * return the next one it does have. It traverses from the top
     * left to right frames, and top to bottom for each column of
     * frames. It handles all the subframes for a frame at one time.
     * 
     * @return OMRaster image.
     */
    public OMRaster getNextImage() {

        OMRaster subframe = null;

        // Subframe coordinates and height and width
        // upper left, lower right
        double sf_ullat, sf_ullon, sf_lrlat, sf_lrlon;
        long sf_width = SF_PIXEL_HW;
        long sf_height = SF_PIXEL_HW;

        if (Debug.debugging("dted"))
            Debug.output("--- DTEDCacheHandler: getNextImage:");

        while (true) {

            if (firstImageReturned == true) {
                frameLon = frameLeft;
                frameLat = frameDown;
                subx = 0;
                suby = 0;
                newframe = true;
                firstImageReturned = false;
            } else {
                if (frame != null && subx < numXSubframes) {
                    // update statics to look for next subframe
                    if (suby < numYSubframes - 1)
                        suby++;
                    else {
                        suby = 0;
                        subx++;
                    }
                } else if (frameLon < frameRight) {
                    // update statics to look for next frame
                    subx = 0;
                    suby = 0;
                    if (frameLat < frameUp)
                        frameLat++;
                    else {
                        frameLat = frameDown;
                        frameLon++;
                    }
                    newframe = true;
                } else { // bounds exceeded, all done
                    return (OMRaster) null;
                }
            }

            if (newframe && frameLon < frameRight) {
                if (Debug.debugging("dted"))
                    Debug.output(" gni: Getting new frame Lat = " + frameLat
                            + " Lon = " + frameLon);

                frame = frameCache.get(frameLat, frameLon, dfsi.dtedLevel);
            }

            //  Figure out subframe lat/lon and height/width
            if (frame != null) {

                newframe = false;
                if (subx == (numXSubframes - 1))
                    sf_width = lastSubframeWidth;
                if (suby == (numYSubframes - 1))
                    sf_height = lastSubframeHeight;
                // width/height degrees are spacers - degrees to
                // subframe within the frame. sf_height/width_degrees
                // are the lat/lon of the frame corner.
                double sf_width_degrees = (double) sf_width * xPixInterval;
                double sf_height_degrees = (double) sf_height * yPixInterval;
                double width_degrees = (double) SF_PIXEL_HW * xPixInterval;
                double height_degrees = (double) SF_PIXEL_HW * yPixInterval;

                sf_ullat = (double) (frameLat + 1.0)
                        - ((double) suby * height_degrees);
                sf_ullon = (double) frameLon + ((double) subx * width_degrees);
                sf_lrlat = (double) (frameLat + 1.0)
                        - ((double) suby * height_degrees) - sf_height_degrees;
                sf_lrlon = (double) frameLon + ((double) subx * width_degrees)
                        + sf_width_degrees;

                if ((ulCoords.getLatitude() > sf_lrlat && lrCoords.getLatitude() < sf_ullat)
                        &&

                        (ulCoords.getLongitude() < sf_lrlon && lrCoords.getLongitude() > sf_ullon)
                        &&

                        subx < numXSubframes) {

                    dfsi.height = (int) sf_height;
                    dfsi.width = (int) sf_width;
                    dfsi.lon = (float) sf_ullon;
                    dfsi.lat = (float) sf_ullat;
                    dfsi.subx = subx;
                    dfsi.suby = suby;

                    if (Debug.debugging("dteddetail")) {
                        Debug.output(" gni: Looking for Subframe " + subx
                                + ", " + suby);
                    }

                    subframe = frame.getSubframeOMRaster(dfsi, colortable);

                    if (subframe != null) {
                        if (Debug.debugging("dted")) {
                            Debug.output(" gni: Subframe " + subx + ", " + suby
                                    + " found :)");
                        }
                        return subframe;
                    }
                } else if (Debug.debugging("dteddetail")) {
                    Debug.output(" gni: Subframe " + subx + ", " + suby
                            + " didn't meet screen criteria");
                }
            }
            sf_width = SF_PIXEL_HW;
            sf_height = SF_PIXEL_HW;
        }
    }

}