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
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
import React from 'react';
import PropTypes from 'prop-types';
import classNames from 'classnames';
export default class ImageLoader extends React.PureComponent {
static propTypes = {
alt: PropTypes.string,
src: PropTypes.string.isRequired,
previewSrc: PropTypes.string.isRequired,
width: PropTypes.number,
height: PropTypes.number,
}
static defaultProps = {
alt: '',
width: null,
height: null,
};
state = {
loading: true,
error: false,
}
removers = [];
get canvasContext() {
if (!this.canvas) {
return null;
}
this._canvasContext = this._canvasContext || this.canvas.getContext('2d');
return this._canvasContext;
}
componentDidMount () {
this.loadImage(this.props);
}
componentWillReceiveProps (nextProps) {
if (this.props.src !== nextProps.src) {
this.loadImage(nextProps);
}
}
loadImage (props) {
this.removeEventListeners();
this.setState({ loading: true, error: false });
Promise.all([
this.loadPreviewCanvas(props),
this.hasSize() && this.loadOriginalImage(props),
].filter(Boolean))
.then(() => {
this.setState({ loading: false, error: false });
this.clearPreviewCanvas();
})
.catch(() => this.setState({ loading: false, error: true }));
}
loadPreviewCanvas = ({ previewSrc, width, height }) => new Promise((resolve, reject) => {
const image = new Image();
const removeEventListeners = () => {
image.removeEventListener('error', handleError);
image.removeEventListener('load', handleLoad);
};
const handleError = () => {
removeEventListeners();
reject();
};
const handleLoad = () => {
removeEventListeners();
this.canvasContext.drawImage(image, 0, 0, width, height);
resolve();
};
image.addEventListener('error', handleError);
image.addEventListener('load', handleLoad);
image.src = previewSrc;
this.removers.push(removeEventListeners);
})
clearPreviewCanvas () {
const { width, height } = this.canvas;
this.canvasContext.clearRect(0, 0, width, height);
}
loadOriginalImage = ({ src }) => new Promise((resolve, reject) => {
const image = new Image();
const removeEventListeners = () => {
image.removeEventListener('error', handleError);
image.removeEventListener('load', handleLoad);
};
const handleError = () => {
removeEventListeners();
reject();
};
const handleLoad = () => {
removeEventListeners();
resolve();
};
image.addEventListener('error', handleError);
image.addEventListener('load', handleLoad);
image.src = src;
this.removers.push(removeEventListeners);
});
removeEventListeners () {
this.removers.forEach(listeners => listeners());
this.removers = [];
}
hasSize () {
const { width, height } = this.props;
return typeof width === 'number' && typeof height === 'number';
}
setCanvasRef = c => {
this.canvas = c;
}
render () {
const { alt, src, width, height } = this.props;
const { loading } = this.state;
const className = classNames('image-loader', {
'image-loader--loading': loading,
'image-loader--amorphous': !this.hasSize(),
});
return (
<div className={className}>
<canvas
className='image-loader__preview-canvas'
width={width}
height={height}
ref={this.setCanvasRef}
style={{ opacity: loading ? 1 : 0 }}
/>
{!loading && (
<img
alt={alt}
className='image-loader__img'
src={src}
width={width}
height={height}
/>
)}
</div>
);
}
}
|
