File	Doc	Category	Size	Date	Package
LinearGradientPaintContext.java	API Doc	Java SE 6 API	5661	Tue Jun 10 00:25:16 BST 2008	java.awt

LinearGradientPaintContext

• java.lang.Object
  • java.awt.MultipleGradientPaintContext

Fields Summary
private float	dgdX The following invariants are used to process the gradient value from a device space coordinate, (X, Y): g(X, Y) = dgdX*X + dgdY*Y + gc
private float	dgdY
private float	gc

Constructors Summary

LinearGradientPaintContext(LinearGradientPaint paint, ColorModel cm, Rectangle deviceBounds, Rectangle2D userBounds, AffineTransform t, RenderingHints hints, Point2D start, Point2D end, float[] fractions, Color[] colors, java.awt.MultipleGradientPaint.CycleMethod cycleMethod, java.awt.MultipleGradientPaint.ColorSpaceType colorSpace) Constructor for LinearGradientPaintContext. param paint the {@code LinearGradientPaint} from which this context is created param cm {@code ColorModel} that receives the Paint data. This is used only as a hint. param deviceBounds the device space bounding box of the graphics primitive being rendered param userBounds the user space bounding box of the graphics primitive being rendered param t the {@code AffineTransform} from user space into device space (gradientTransform should be concatenated with this) param hints the hints that the context object uses to choose between rendering alternatives param dStart gradient start point, in user space param dEnd gradient end point, in user space param fractions the fractions specifying the gradient distribution param colors the gradient colors param cycleMethod either NO_CYCLE, REFLECT, or REPEAT param colorSpace which colorspace to use for interpolation, either SRGB or LINEAR_RGB super(paint, cm, deviceBounds, userBounds, t, hints, fractions, colors, cycleMethod, colorSpace); // A given point in the raster should take on the same color as its // projection onto the gradient vector. // Thus, we want the projection of the current position vector // onto the gradient vector, then normalized with respect to the // length of the gradient vector, giving a value which can be mapped // into the range 0-1. // projection = // currentVector dot gradientVector / length(gradientVector) // normalized = projection / length(gradientVector) float startx = (float)start.getX(); float starty = (float)start.getY(); float endx = (float)end.getX(); float endy = (float)end.getY(); float dx = endx - startx; // change in x from start to end float dy = endy - starty; // change in y from start to end float dSq = dx*dx + dy*dy; // total distance squared // avoid repeated calculations by doing these divides once float constX = dx/dSq; float constY = dy/dSq; // incremental change along gradient for +x dgdX = a00*constX + a10*constY; // incremental change along gradient for +y dgdY = a01*constX + a11*constY; // constant, incorporates the translation components from the matrix gc = (a02-startx)*constX + (a12-starty)*constY;

Methods Summary

protected void

fillRaster(int[] pixels, int off, int adjust, int x, int y, int w, int h) Return a Raster containing the colors generated for the graphics operation. This is where the area is filled with colors distributed linearly. param x,y,w,h the area in device space for which colors are generated. // current value for row gradients float g = 0; // used to end iteration on rows int rowLimit = off + w; // constant which can be pulled out of the inner loop float initConst = (dgdX*x) + gc; for (int i = 0; i < h; i++) { // for every row // initialize current value to be start g = initConst + dgdY*(y+i); while (off < rowLimit) { // for every pixel in this row // get the color pixels[off++] = indexIntoGradientsArrays(g); // incremental change in g g += dgdX; } // change in off from row to row off += adjust; //rowlimit is width + offset rowLimit = off + w; }