Re: [OpenMap Users] Moving the map like Google

From: F.Bayliss <bayliss_at_alcatel-lucent.com>
Date: Thu, 10 Apr 2008 09:21:19 -0400

Thanks Rob.

I've tried variations of #1 and #2 and the delay in creating the image isn't acceptable by management. Except for the delay it worked well. I've thought about #3 but wasn't sure of the best approach. If they still insist on having me work on this I'll look into this idea.

Thanks
Frank


Rob Ratcliff wrote:

I think Google maps just loads image tiles around the current projection so when you translate, the images are already there and makes it look smooth.

Here are few ideas you might try:

1.) cache the image buffer between panel resizes and reuse it

2.) create a layer or mousemode that takes a image snapshot of the current map and then translate the image to the new locations during the mouse drag and the notify the layers to update after the mouse button is released or modify each layer to draw a cached offscreen image during mouse movements and recalculate upon mouse up.

3.) If you don't like the the idea of translating an image with the resulting unrendered gaps that show up, you could keep track of dirty areas and the only recalulate those regions. NetBeans chart code had some high performance ways of translating the chart in time and only updating the new deltas which may be useful (with some surgery):

http://www.netbeans.org/source/browse/profiler/libs/jfluid-ui/src/org/netbeans/lib/profiler/ui/charts/SynchronousXYChart.java?rev=1.1&view=auto&content-type=text/vnd.viewcvs-markup

// draws scaled chart from provided viewOffsetX
    private void drawChartFromOffset(Graphics2D g2, long offsetX) {

...

                        if ((copyWidth > 0) && (dirtyWidth > 0) && (chartHeight > 0)) {
                            // copy not-changed-areas to the left
                            if (copyAccel == COPY_ACCEL_RASTER) {
                                // BufferedImage.getRaster().setDataElements() used, seems to have better performance on Windows (HW acceleration)
                                int rasterWidth = offScreenImage.getRaster().getWidth();
                                int rasterHeight = offScreenImage.getRaster().getHeight();
                                int startX = chartInsets.left + dirtyWidth;
                                int startY = chartInsets.top;

                                if ((startX >= 0) && ((startX + copyWidth) <= rasterWidth) && (startY >= 0)
                                        && ((startY + chartHeight) <= rasterHeight) && (chartInsets.left >= 0)
                                        && ((chartInsets.left + copyWidth) <= rasterWidth) && (chartInsets.top >= 0)
                                        && ((chartInsets.top + chartHeight) <= rasterHeight)) {
                                    Raster raster = offScreenImage.getRaster()
                                                                  .createWritableChild(startX, startY, copyWidth, chartHeight, 0,
                                                                                       0, null);
                                    offScreenImage.getRaster().setDataElements(chartInsets.left, chartInsets.top, raster);
                                }
                            } else {
                                // Graphics.copyArea() used, optimal for UNIXes, works well also for Windows (default)
                                g2.copyArea(chartInsets.left + dirtyWidth, chartInsets.top, copyWidth, chartHeight, -dirtyWidth, 0);
                            }
                        }

  

F.Bayliss wrote:

Hello,

I've been asked by my upper management to once again mimic the way Google allows the user to move the map. I've spent a lot of time on this, too much, and I don't see anyway it can work. I have several, several layers and the time it takes to process and draw a map movement event is slow and that results in a choppy map picture. I've tried several approaches, the best being drawing the map to an image buffer and replacing the map with that, letting them move what they think is the map. But this isn't acceptable because it takes time to create the image. I was hoping the experts had a better idea.

Thanks
Frank

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-- [To unsubscribe to this list send an email to "majdart_at_bbn.com" with the following text in the BODY of the message "unsubscribe openmap-users"] Received on Thu Apr 10 2008 - 09:33:10 EDT