protected void determineCanvasLayout() {
// Find the spatial extent of the tiles needed to cover the desired extent
srcRectangle = gridSubset.getCoverageIntersection(srcIdx, reqBounds);
srcBounds = gridSubset.boundsFromRectangle(srcRectangle);
// We now have the complete area, lets figure out our offsets
// Positive means that there is blank space to the first tile,
// negative means we will not use the entire tile
boundOfs.left = srcBounds.getMinX() - reqBounds.getMinX();
boundOfs.bottom = srcBounds.getMinY() - reqBounds.getMinY();
boundOfs.right = reqBounds.getMaxX() - srcBounds.getMaxX();
boundOfs.top = reqBounds.getMaxY() - srcBounds.getMaxY();
canvasSize[0] = (int) Math.round(reqBounds.getWidth() / this.srcResolution);
canvasSize[1] = (int) Math.round(reqBounds.getHeight() / this.srcResolution);
PixelOffsets naiveOfs = new PixelOffsets();
// Calculate the corresponding pixel offsets. We'll stick to sane,
// i.e. bottom left, coordinates at this point
naiveOfs.left = (int) Math.round(boundOfs.left / this.srcResolution);
naiveOfs.bottom = (int) Math.round(boundOfs.bottom / this.srcResolution);
naiveOfs.right = (int) Math.round(boundOfs.right / this.srcResolution);
naiveOfs.top = (int) Math.round(boundOfs.top / this.srcResolution);
// Find the offsets on the opposite sides. This is dependent of how the first two were rounded.
// First, find a tile boundary near the canvas edge, then make sure it's on the correct
// side to match the corresponding boundOfs, then take the modulo of the naive rounding
// based on the boundOfs, then subtract the two and apply the difference to the boundOfs.
int tileWidth = this.gridSubset.getTileWidth();
int tileHeight = this.gridSubset.getTileHeight();
canvOfs.left = naiveOfs.left;
canvOfs.bottom = naiveOfs.bottom;
canvOfs.right = (canvasSize[0] - canvOfs.left) % tileWidth; // Find nearby tile boundary
canvOfs.right =
(Integer.signum(naiveOfs.right) * tileWidth + canvOfs.right)
% tileWidth; // Ensure same sign as naive calculation
canvOfs.right =
canvOfs.right
- (naiveOfs.right % tileWidth)
+ naiveOfs.right; // Find adjustment from naive and apply to naive calculation
canvOfs.top = (canvasSize[1] - canvOfs.bottom) % tileHeight; // Find nearby tile boundary
canvOfs.top =
(Integer.signum(naiveOfs.top) * tileHeight + canvOfs.top)
% tileHeight; // Ensure same sign as naive calculation
canvOfs.top =
canvOfs.top
- (naiveOfs.top % tileHeight)
+ naiveOfs.top; // Find adjustment from naive and apply to naive calculation
// postconditions
assert Math.abs(canvOfs.left - naiveOfs.left) <= 1;
assert Math.abs(canvOfs.bottom - naiveOfs.bottom) <= 1;
assert Math.abs(canvOfs.right - naiveOfs.right) <= 1;
assert Math.abs(canvOfs.top - naiveOfs.top) <= 1;
if (log.isDebugEnabled()) {
log.debug("intersection rectangle: " + Arrays.toString(srcRectangle));
log.debug("intersection bounds: " + srcBounds + " (" + reqBounds + ")");
log.debug(
"Bound offsets: "
+ Arrays.toString(
new double[] {boundOfs.left, boundOfs.bottom, boundOfs.right, boundOfs.top}));
log.debug(
"Canvas size: " + Arrays.toString(canvasSize) + "(" + reqWidth + "," + reqHeight + ")");
log.debug(
"Canvas offsets: "
+ Arrays.toString(
new int[] {canvOfs.left, canvOfs.bottom, canvOfs.right, canvOfs.top}));
}
}
