1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
|
/* ldgallery - A static generator which turns a collection of tagged
-- pictures into a searchable web gallery.
--
-- Copyright (C) 2020 Pacien TRAN-GIRARD
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU Affero General Public License as
-- published by the Free Software Foundation, either version 3 of the
-- License, or (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU Affero General Public License for more details.
--
-- You should have received a copy of the GNU Affero General Public License
-- along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
// polyfill still required for IE and Safari, see https://caniuse.com/#feat=resizeobserver
import ResizeObserver from "resize-observer-polyfill";
import "hammerjs";
/**
* Mousewheel and pinch zoom handler.
*/
export default class LdZoom {
readonly containerElement: HTMLDivElement;
readonly imageElement: HTMLImageElement;
readonly pictureProperties: Gallery.PictureProperties;
readonly maxScaleFactor: number;
readonly scrollZoomSpeed: number;
scaleFactor: number = 0.0;
constructor(
containerElement: HTMLDivElement,
imageElement: HTMLImageElement,
pictureProperties: Gallery.PictureProperties,
maxScaleFactor: number,
scrollZoomSpeed: number
) {
this.containerElement = containerElement;
this.imageElement = imageElement;
this.pictureProperties = pictureProperties;
this.maxScaleFactor = maxScaleFactor;
this.scrollZoomSpeed = scrollZoomSpeed;
}
/**
* Register event listeners.
*/
public install() {
this.updateImageScale(this.scaleFactor);
new ResizeObserver(() => {
this.updateImageScale(this.scaleFactor);
}).observe(this.containerElement);
this.containerElement.addEventListener("wheel", wheelEvent => {
wheelEvent.preventDefault();
const scaleFactor = this.scaleFactor - Math.sign(wheelEvent.deltaY) * this.scrollZoomSpeed;
this.zoom(wheelEvent.offsetX, wheelEvent.offsetY, scaleFactor);
});
const pinchListener = new Hammer(this.containerElement);
pinchListener.get("pinch").set({ enable: true });
this.installPinchHandler(pinchListener);
}
private installPinchHandler(pinchListener: HammerManager) {
let startScaleFactor = 0.0;
pinchListener.on("pinchstart", (pinchEvent: HammerInput) => {
startScaleFactor = this.scaleFactor;
});
pinchListener.on("pinchmove", (pinchEvent: HammerInput) => {
const focusX = pinchEvent.center.x + this.containerElement.scrollLeft;
const focusY = pinchEvent.center.y + this.containerElement.scrollTop;
const scaleFactor = pinchEvent.scale * startScaleFactor;
this.zoom(focusX, focusY, scaleFactor);
});
}
/**
* Returns the picture resolution as it should be displayed.
*/
private getDisplayResolution(): Gallery.Resolution {
return {
width: this.pictureProperties.resolution.width * this.scaleFactor,
height: this.pictureProperties.resolution.height * this.scaleFactor,
};
}
/**
* Applies scaling to the DOM image element.
* To call after internal intermediate computations because DOM properties aren't stable.
*/
private resizeImageElement() {
const imageDim = this.getDisplayResolution();
this.imageElement.width = imageDim.width;
this.imageElement.height = imageDim.height;
}
/**
* Centers the image element inside its container if it fits, or stick to the top and left borders otherwise.
* It's depressingly hard to do in pure CSS…
*/
private recenterImageElement() {
const imageDim = this.getDisplayResolution();
const marginLeft = Math.max((this.containerElement.clientWidth - imageDim.width) / 2, 0);
const marginTop = Math.max((this.containerElement.clientHeight - imageDim.height) / 2, 0);
this.imageElement.style.marginLeft = `${marginLeft}px`;
this.imageElement.style.marginTop = `${marginTop}px`;
}
private zoom(focusX: number, focusY: number, scaleFactor: number) {
const imageDim = this.getDisplayResolution();
const ratioX = focusX / imageDim.width;
const ratioY = focusY / imageDim.height;
this.updateImageScale(Math.min(scaleFactor, this.maxScaleFactor));
const newImageDim = this.getDisplayResolution();
this.containerElement.scrollLeft -= focusX - ratioX * newImageDim.width;
this.containerElement.scrollTop -= focusY - ratioY * newImageDim.height;
}
private updateImageScale(newScaleFactor: number) {
const horizontalFillRatio = this.containerElement.clientWidth / this.pictureProperties.resolution.width;
const verticalFillRatio = this.containerElement.clientHeight / this.pictureProperties.resolution.height;
const minScaleFactor = Math.min(horizontalFillRatio, verticalFillRatio, 1.0);
this.scaleFactor = Math.max(newScaleFactor, minScaleFactor);
this.resizeImageElement();
this.recenterImageElement();
}
}
|