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Use fewer multiplications in JpegImage._convertCmykToRgb

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*Note:* This is inspired by PR 5473, which made similar changes for another kind of JPEG data.

Since the implementation in `src/core/jpg.js` only supports 8-bit data, as opposed to similar code in `src/core/colorspace.js`, the computations can be further simplified since the `scale` is always constant.
By updating the coefficients, effectively inlining the `scale`, we'll thus avoid *four* multiplications for each loop iteration.

Unfortunately I wasn't able, based on a quick look through the test-files, to find a sufficiently *large* CMYK JPEG image in order for these changes to really show up in benchmark results. However, when testing the `cmykjpeg.pdf` manually there's a total of `120 000` fewer multiplication with this patch.
This commit is contained in:
Jonas Jenwald 2020-01-29 18:20:26 +01:00
parent 89d345c7bd
commit ce4f41d06a
1 changed files with 43 additions and 42 deletions
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85
src/core/jpg.js
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@ -1283,67 +1283,68 @@ var JpegImage = (function JpegImageClosure() {
_convertCmykToRgb: function convertCmykToRgb(data) {
var c, m, y, k;
var offset = 0;
var scale = 1 / 255;
for (var i = 0, length = data.length; i < length; i += 4) {
c = data[i] * scale;
m = data[i + 1] * scale;
y = data[i + 2] * scale;
k = data[i + 3] * scale;
c = data[i];
m = data[i + 1];
y = data[i + 2];
k = data[i + 3];
data[offset++] =
255 +
c *
(-4.387332384609988 * c +
54.48615194189176 * m +
18.82290502165302 * y +
212.25662451639585 * k -
285.2331026137004) +
(-0.00006747147073602441 * c +
0.0008379262121013727 * m +
0.0002894718188643294 * y +
0.003264231057537806 * k -
1.1185611867203937) +
m *
(1.7149763477362134 * m -
5.6096736904047315 * y -
17.873870861415444 * k -
5.497006427196366) +
(0.000026374107616089405 * m -
0.00008626949158638572 * y -
0.0002748769067499491 * k -
0.02155688794978967) +
y *
(-2.5217340131683033 * y -
21.248923337353073 * k +
17.5119270841813) -
k * (21.86122147463605 * k + 189.48180835922747);
(-0.00003878099212869363 * y -
0.0003267808279485286 * k +
0.0686742238595345) -
k * (0.0003361971776183937 * k + 0.7430659151342254);
data[offset++] =
255 +
c *
(8.841041422036149 * c +
60.118027045597366 * m +
6.871425592049007 * y +
31.159100130055922 * k -
79.2970844816548) +
(0.00013596372813588848 * c +
0.000924537132573585 * m +
0.00010567359618683593 * y +
0.0004791864687436512 * k -
0.3109689587515875) +
m *
(-15.310361306967817 * m +
17.575251261109482 * y +
131.35250912493976 * k -
190.9453302588951) +
(-0.00023545346108370344 * m +
0.0002702845253534714 * y +
0.0020200308977307156 * k -
0.7488052167015494) +
y *
(4.444339102852739 * y + 9.8632861493405 * k - 24.86741582555878) -
k * (20.737325471181034 * k + 187.80453709719578);
(0.00006834815998235662 * y +
0.00015168452363460973 * k -
0.09751927774728933) -
k * (0.00031891311758832814 * k + 0.7364883807733168);
data[offset++] =
255 +
c *
(0.8842522430003296 * c +
8.078677503112928 * m +
30.89978309703729 * y -
0.23883238689178934 * k -
14.183576799673286) +
(0.000013598650411385307 * c +
0.00012423956175490851 * m +
0.0004751985097583589 * y -
0.0000036729317476630422 * k -
0.05562186980264034) +
m *
(10.49593273432072 * m +
63.02378494754052 * y +
50.606957656360734 * k -
112.23884253719248) +
(0.00016141380598724676 * m +
0.0009692239130725186 * y +
0.0007782692450036253 * k -
0.44015232367526463) +
y *
(0.03296041114873217 * y +
115.60384449646641 * k -
193.58209356861505) -
k * (22.33816807309886 * k + 180.12613974708367);
(5.068882914068769e-7 * y +
0.0017778369011375071 * k -
0.7591454649749609) -
k * (0.0003435319965105553 * k + 0.7063770186160144);
}
// Ensure that only the converted RGB data is returned.
return data.subarray(0, offset);