Re: Problem dealing with image transparency

Jess,

What happens when you don't scale the image? Does the transparency
work? I'm wondering if the smooth scaling algorithm is setting the
transparent pixels to opaque...

- Don

On Tuesday, July 10, 2001, at 06:38 PM, Jess Miller wrote:

> I have a layer (Don - you helped with this some time ago) that
> allows you to "register" an image to a map using corner points.
> The layer rescales the OMRaster (holding the image) as necessary.
> Problem is, if the image is a GIF with transparent pixels, they
> are turned to white by the time the image is displayed. Any ideas?
> Here's the code for the layer:
>
>
> package ipt.tas.map.openmap;
>
> import ipt.util.*;
>
> import com.bbn.openmap.*;
> import com.bbn.openmap.event.*;
> import com.bbn.openmap.omGraphics.*;
> import com.bbn.openmap.proj.*;
> import com.bbn.openmap.image.BufferedImageHelper;
> import com.bbn.openmap.image.ImageHelper;
>
> import java.awt.*;
> import java.net.*;
> import java.awt.image.*;
> import java.util.*;
> import javax.swing.*;
>
> public class GeoRefImageLayer extends Layer
> {
> protected String mImageFileName;
> protected float mULLat;
> protected float mULLon;
> protected float mLRLat;
> protected float mLRLon;
> protected OMRaster mOMRaster;
> protected ImageIcon mImageIcon;
> protected boolean mShowBoundingBox = false;
> protected OMRect mOMRect;
> protected int mLastImageHeight;
> protected int mLastImageWidth;
> protected int mLastX;
> protected int mLastY;
>
> public GeoRefImageLayer() {
> }
>
> public void setProperties(String prefix, Properties props) {
> super.setProperties(prefix, props);
> // get the image
> mImageFileName = props.getProperty(prefix + ".image");
>
> // show coverage?
> mShowBoundingBox = new Boolean(props.getProperty(prefix +
> ".showBoundingBox")).booleanValue();
> // get the upper left corner point lat/lon
> mULLat = getFloatProperty(prefix + ".upperLeftLatitude", props);
> mULLon = getFloatProperty(prefix + ".upperLeftLongitude",
> props);
> mLRLat = getFloatProperty(prefix + ".lowerRightLatitude",
> props);
> mLRLon = getFloatProperty(prefix + ".lowerRightLongitude",
> props);
> if (Debug.isEnabled(this)) {
> Debug.println(getClass().getName() + " mULLat = " + mULLat +
> ", mULLon = " + mULLon);
> Debug.println(getClass().getName() + " mLRLat = " + mLRLat +
> ", mLRLon = " + mLRLon);
> }
> }
>
> protected float getFloatProperty(String name, Properties props) {
> try {
> String s = props.getProperty(name);
> if (s == null) {
> mImageFileName = null;
> return 0;
> }
> Float x = new Float(s);
> return x.floatValue();
> }
> catch (Exception e) {
> mImageFileName = null;
> return 0;
> }
> }
>
> public void projectionChanged(ProjectionEvent evt) {
> Projection proj = evt.getProjection();
>
> if (Debug.isEnabled(this)) {
> Debug.println(getClass().getName() + ".projectionChanged
> ");
> }
>
> if (mOMRaster == null){
> if (mImageFileName != null) {
> try {
> BufferedImage bi =
> BufferedImageHelper.getBufferedImage(mImageFileName, 0, 0, -1, -1);
> int height = bi.getHeight();
> int width = bi.getWidth();
>
> PixelGrabber pg = new PixelGrabber(bi, 0, 0, width,
> height, true);
> int[] pixels = ImageHelper.grabPixels(pg);
>
> mOMRaster = new OMRaster(mULLat, mULLon, width,
> height, pixels);
> } catch (InterruptedException ie){
> mOMRaster = null;
> }
> }
> }
>
> // recompute image scaling
> if (mOMRaster != null) {
>
> Point pt1 = proj.forward(mULLat, mULLon);
> Point pt2 = proj.forward(mLRLat, mLRLon);
>
> int imageHeight = pt2.y - pt1.y;
> int imageWidth = pt2.x - pt1.x;
>
> if (Debug.isEnabled(this)) {
> Debug.println(getClass().getName() + " width = " +
> imageWidth +
> ", height = " + imageHeight);
> }
>
> boolean rescaled = false;
>
> //if (imageWidth != mLastImageWidth || imageHeight !=
> mLastImageHeight) {
> mOMRaster.scaleTo(imageWidth, imageHeight,
> OMRasterObject.SMOOTH_SCALING);
> mLastImageWidth = imageWidth;
> mLastImageHeight = imageHeight;
> rescaled = true;
> //}
>
> //if (rescaled || pt1.x != mLastX || pt1.y != mLastY) {
> mOMRaster.generate(proj);
> mLastX = pt1.x;
> mLastY = pt1.y;
> //}
> }
> if (mShowBoundingBox) {
> if (mOMRect == null) {
> mOMRect = new OMRect(mULLat, mULLon, mLRLat, mLRLon,
> OMGraphic.LINETYPE_STRAIGHT);
> }
> mOMRect.generate(proj);
> }
>
> repaint();
> }
>
> public void paint(Graphics g) {
> fireStatusUpdate(LayerStatusEvent.START_WORKING);
> if (mOMRaster != null) {
> mOMRaster.render(g);
> }
> if (mOMRect != null) {
> mOMRect.render(g);
> }
> fireStatusUpdate(LayerStatusEvent.FINISH_WORKING);
> }
> }
>
> --
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>

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