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
|
const bmp = require('bmp-js');
const fileType = require('file-type');
/**
* setImage
*
* @name setImage
* @function set image in tesseract for recognition
* @access public
*/
module.exports = (TessModule, api, image) => {
const buf = (image instanceof Uint8Array) ? Buffer.from(image) : null;
const type = buf ? fileType(buf) : null;
let bytesPerPixel = 0;
let data = null;
let pix = null;
let w = 0;
let h = 0;
if (image instanceof ImageData) {
// The pixel format of ImageData is RGBA and technically
// Tesseract is expecting ABGR, but it does not seem to matter
// in practice, so to save effort the bytes are not rearranged.
data = TessModule._malloc(image.data.byteLength);
TessModule.HEAPU8.set(image.data, data);
w = image.width;
h = image.height;
bytesPerPixel = 4;
} else if (buf && type && type.mime === 'image/bmp') {
/*
* Although leptonica should support reading bmp, there is a bug of "compressed BMP files".
* As there is no solution, we need to use bmp-js for now.
* @see https://groups.google.com/forum/#!topic/tesseract-ocr/4mPD9zTxdxE
*/
const bmpBuf = bmp.decode(buf);
data = TessModule._malloc(bmpBuf.data.length * Uint8Array.BYTES_PER_ELEMENT);
TessModule.HEAPU8.set(bmpBuf.data, data);
w = bmpBuf.width;
h = bmpBuf.height;
bytesPerPixel = 4;
} else if (buf) {
const ptr = TessModule._malloc(buf.length * Uint8Array.BYTES_PER_ELEMENT);
TessModule.HEAPU8.set(buf, ptr);
pix = TessModule._pixReadMem(ptr, buf.length);
if (TessModule.getValue(pix + (7 * 4), 'i32') === 0) {
/*
* Set a yres default value to prevent warning from tesseract
* See kMinCredibleResolution in tesseract/src/ccstruct/publictypes.h
*/
TessModule.setValue(pix + (7 * 4), 300, 'i32');
}
[w, h] = Array(2).fill(0)
.map((v, idx) => (
TessModule.getValue(pix + (idx * 4), 'i32')
));
} else {
throw Error('Unsupported image data container');
}
/*
* As some image format (ex. bmp) is not supported natiely by tesseract,
* sometimes it will not return pix directly, but data and bytesPerPixel
* for another SetImage usage.
*
*/
if (data === null) {
api.SetImage(pix);
} else {
api.SetImage(data, w, h, bytesPerPixel, w * bytesPerPixel);
}
return data === null ? pix : data;
};
|
