pdf.js.mirror/src/display/page_viewport.js

/* Copyright 2015 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { shadow, Util } from "../shared/util.js";

/**
 * @typedef {Object} PageViewportParameters
 * @property {Array<number>} viewBox - The xMin, yMin, xMax and
 *   yMax coordinates.
 * @property {number} userUnit - The size of units.
 * @property {number} scale - The scale of the viewport.
 * @property {number} rotation - The rotation, in degrees, of the viewport.
 * @property {number} [offsetX] - The horizontal, i.e. x-axis, offset. The
 *   default value is `0`.
 * @property {number} [offsetY] - The vertical, i.e. y-axis, offset. The
 *   default value is `0`.
 * @property {boolean} [dontFlip] - If true, the y-axis will not be flipped.
 *   The default value is `false`.
 */

/**
 * @typedef {Object} PageViewportCloneParameters
 * @property {number} [scale] - The scale, overriding the one in the cloned
 *   viewport. The default value is `this.scale`.
 * @property {number} [rotation] - The rotation, in degrees, overriding the one
 *   in the cloned viewport. The default value is `this.rotation`.
 * @property {number} [offsetX] - The horizontal, i.e. x-axis, offset.
 *   The default value is `this.offsetX`.
 * @property {number} [offsetY] - The vertical, i.e. y-axis, offset.
 *   The default value is `this.offsetY`.
 * @property {boolean} [dontFlip] - If true, the x-axis will not be flipped.
 *   The default value is `false`.
 */

/**
 * PDF page viewport created based on scale, rotation and offset.
 */
class PageViewport {
  /**
   * @param {PageViewportParameters}
   */
  constructor({
    viewBox,
    userUnit,
    scale,
    rotation,
    offsetX = 0,
    offsetY = 0,
    dontFlip = false,
  }) {
    this.viewBox = viewBox;
    this.userUnit = userUnit;
    this.scale = scale;
    this.rotation = rotation;
    this.offsetX = offsetX;
    this.offsetY = offsetY;

    scale *= userUnit; // Take the userUnit into account.

    // creating transform to convert pdf coordinate system to the normal
    // canvas like coordinates taking in account scale and rotation
    const centerX = (viewBox[2] + viewBox[0]) / 2;
    const centerY = (viewBox[3] + viewBox[1]) / 2;
    let rotateA, rotateB, rotateC, rotateD;
    // Normalize the rotation, by clamping it to the [0, 360) range.
    rotation %= 360;
    if (rotation < 0) {
      rotation += 360;
    }
    switch (rotation) {
      case 180:
        rotateA = -1;
        rotateB = 0;
        rotateC = 0;
        rotateD = 1;
        break;
      case 90:
        rotateA = 0;
        rotateB = 1;
        rotateC = 1;
        rotateD = 0;
        break;
      case 270:
        rotateA = 0;
        rotateB = -1;
        rotateC = -1;
        rotateD = 0;
        break;
      case 0:
        rotateA = 1;
        rotateB = 0;
        rotateC = 0;
        rotateD = -1;
        break;
      default:
        throw new Error(
          "PageViewport: Invalid rotation, must be a multiple of 90 degrees."
        );
    }

    if (dontFlip) {
      rotateC = -rotateC;
      rotateD = -rotateD;
    }

    let offsetCanvasX, offsetCanvasY;
    let width, height;
    if (rotateA === 0) {
      offsetCanvasX = Math.abs(centerY - viewBox[1]) * scale + offsetX;
      offsetCanvasY = Math.abs(centerX - viewBox[0]) * scale + offsetY;
      width = (viewBox[3] - viewBox[1]) * scale;
      height = (viewBox[2] - viewBox[0]) * scale;
    } else {
      offsetCanvasX = Math.abs(centerX - viewBox[0]) * scale + offsetX;
      offsetCanvasY = Math.abs(centerY - viewBox[1]) * scale + offsetY;
      width = (viewBox[2] - viewBox[0]) * scale;
      height = (viewBox[3] - viewBox[1]) * scale;
    }
    // creating transform for the following operations:
    // translate(-centerX, -centerY), rotate and flip vertically,
    // scale, and translate(offsetCanvasX, offsetCanvasY)
    this.transform = [
      rotateA * scale,
      rotateB * scale,
      rotateC * scale,
      rotateD * scale,
      offsetCanvasX - rotateA * scale * centerX - rotateC * scale * centerY,
      offsetCanvasY - rotateB * scale * centerX - rotateD * scale * centerY,
    ];

    this.width = width;
    this.height = height;
  }

  /**
   * The original, un-scaled, viewport dimensions.
   * @type {Object}
   */
  get rawDims() {
    const dims = this.viewBox;

    return shadow(this, "rawDims", {
      pageWidth: dims[2] - dims[0],
      pageHeight: dims[3] - dims[1],
      pageX: dims[0],
      pageY: dims[1],
    });
  }

  /**
   * Clones viewport, with optional additional properties.
   * @param {PageViewportCloneParameters} [params]
   * @returns {PageViewport} Cloned viewport.
   */
  clone({
    scale = this.scale,
    rotation = this.rotation,
    offsetX = this.offsetX,
    offsetY = this.offsetY,
    dontFlip = false,
  } = {}) {
    return new PageViewport({
      viewBox: this.viewBox.slice(),
      userUnit: this.userUnit,
      scale,
      rotation,
      offsetX,
      offsetY,
      dontFlip,
    });
  }

  /**
   * Converts PDF point to the viewport coordinates. For examples, useful for
   * converting PDF location into canvas pixel coordinates.
   * @param {number} x - The x-coordinate.
   * @param {number} y - The y-coordinate.
   * @returns {Array} Array containing `x`- and `y`-coordinates of the
   *   point in the viewport coordinate space.
   * @see {@link convertToPdfPoint}
   */
  convertToViewportPoint(x, y) {
    const p = [x, y];
    Util.applyTransform(p, this.transform);
    return p;
  }

  /**
   * Converts viewport coordinates to the PDF location. For examples, useful
   * for converting canvas pixel location into PDF one.
   * @param {number} x - The x-coordinate.
   * @param {number} y - The y-coordinate.
   * @returns {Array} Array containing `x`- and `y`-coordinates of the
   *   point in the PDF coordinate space.
   * @see {@link convertToViewportPoint}
   */
  convertToPdfPoint(x, y) {
    const p = [x, y];
    Util.applyInverseTransform(p, this.transform);
    return p;
  }
}

export { PageViewport };