ducha-qianduan/node_modules/zrender/lib/graphic/helper/subPixelOptimize.js

/**
 * Sub-pixel optimize for canvas rendering, prevent from blur
 * when rendering a thin vertical/horizontal line.
 */
var round = Math.round;
/**
 * Sub pixel optimize line for canvas
 *
 * @param {Object} outputShape The modification will be performed on `outputShape`.
 *                 `outputShape` and `inputShape` can be the same object.
 *                 `outputShape` object can be used repeatly, because all of
 *                 the `x1`, `x2`, `y1`, `y2` will be assigned in this method.
 * @param {Object} [inputShape]
 * @param {number} [inputShape.x1]
 * @param {number} [inputShape.y1]
 * @param {number} [inputShape.x2]
 * @param {number} [inputShape.y2]
 * @param {Object} [style]
 * @param {number} [style.lineWidth] If `null`/`undefined`/`0`, do not optimize.
 */

function subPixelOptimizeLine(outputShape, inputShape, style) {
  if (!inputShape) {
    return;
  }

  var x1 = inputShape.x1;
  var x2 = inputShape.x2;
  var y1 = inputShape.y1;
  var y2 = inputShape.y2;
  outputShape.x1 = x1;
  outputShape.x2 = x2;
  outputShape.y1 = y1;
  outputShape.y2 = y2;
  var lineWidth = style && style.lineWidth;

  if (!lineWidth) {
    return;
  }

  if (round(x1 * 2) === round(x2 * 2)) {
    outputShape.x1 = outputShape.x2 = subPixelOptimize(x1, lineWidth, true);
  }

  if (round(y1 * 2) === round(y2 * 2)) {
    outputShape.y1 = outputShape.y2 = subPixelOptimize(y1, lineWidth, true);
  }
}
/**
 * Sub pixel optimize rect for canvas
 *
 * @param {Object} outputShape The modification will be performed on `outputShape`.
 *                 `outputShape` and `inputShape` can be the same object.
 *                 `outputShape` object can be used repeatly, because all of
 *                 the `x`, `y`, `width`, `height` will be assigned in this method.
 * @param {Object} [inputShape]
 * @param {number} [inputShape.x]
 * @param {number} [inputShape.y]
 * @param {number} [inputShape.width]
 * @param {number} [inputShape.height]
 * @param {Object} [style]
 * @param {number} [style.lineWidth] If `null`/`undefined`/`0`, do not optimize.
 */


function subPixelOptimizeRect(outputShape, inputShape, style) {
  if (!inputShape) {
    return;
  }

  var originX = inputShape.x;
  var originY = inputShape.y;
  var originWidth = inputShape.width;
  var originHeight = inputShape.height;
  outputShape.x = originX;
  outputShape.y = originY;
  outputShape.width = originWidth;
  outputShape.height = originHeight;
  var lineWidth = style && style.lineWidth;

  if (!lineWidth) {
    return;
  }

  outputShape.x = subPixelOptimize(originX, lineWidth, true);
  outputShape.y = subPixelOptimize(originY, lineWidth, true);
  outputShape.width = Math.max(subPixelOptimize(originX + originWidth, lineWidth, false) - outputShape.x, originWidth === 0 ? 0 : 1);
  outputShape.height = Math.max(subPixelOptimize(originY + originHeight, lineWidth, false) - outputShape.y, originHeight === 0 ? 0 : 1);
}
/**
 * Sub pixel optimize for canvas
 *
 * @param {number} position Coordinate, such as x, y
 * @param {number} lineWidth If `null`/`undefined`/`0`, do not optimize.
 * @param {boolean=} positiveOrNegative Default false (negative).
 * @return {number} Optimized position.
 */


function subPixelOptimize(position, lineWidth, positiveOrNegative) {
  if (!lineWidth) {
    return position;
  } // Assure that (position + lineWidth / 2) is near integer edge,
  // otherwise line will be fuzzy in canvas.


  var doubledPosition = round(position * 2);
  return (doubledPosition + round(lineWidth)) % 2 === 0 ? doubledPosition / 2 : (doubledPosition + (positiveOrNegative ? 1 : -1)) / 2;
}

exports.subPixelOptimizeLine = subPixelOptimizeLine;
exports.subPixelOptimizeRect = subPixelOptimizeRect;
exports.subPixelOptimize = subPixelOptimize;