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use fewer multiplications in convertYcckToRgb

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This commit is contained in:
fkaelberer 2014-10-30 10:37:21 +01:00
parent ea719ae805
commit 5fcf3d37a7
1 changed files with 28 additions and 36 deletions
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64
src/core/jpg.js
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@ -503,7 +503,7 @@ var JpegImage = (function jpegImage() {
// stage 3 // stage 3
// Shift v0 by 128.5 << 5 here, so we don't need to shift p0...p7 when // Shift v0 by 128.5 << 5 here, so we don't need to shift p0...p7 when
// converting to UInt8 range later. // converting to UInt8 range later.
v0 = ((v0 + v1 + 1) >> 1) + 4112; v0 = ((v0 + v1 + 1) >> 1) + 4112;
v1 = v0 - v1; v1 = v0 - v1;
t = (v2 * dctSin6 + v3 * dctCos6 + 2048) >> 12; t = (v2 * dctSin6 + v3 * dctCos6 + 2048) >> 12;
@ -897,7 +897,7 @@ var JpegImage = (function jpegImage() {
}, },
_convertYcckToRgb: function convertYcckToRgb(data) { _convertYcckToRgb: function convertYcckToRgb(data) {
var Y, Cb, Cr, k, CbCb, CbCr, CbY, Cbk, CrCr, Crk, CrY, YY, Yk, kk; var Y, Cb, Cr, k;
var offset = 0; var offset = 0;
for (var i = 0, length = data.length; i < length; i += 4) { for (var i = 0, length = data.length; i < length; i += 4) {
Y = data[i]; Y = data[i];
@ -905,43 +905,35 @@ var JpegImage = (function jpegImage() {
Cr = data[i + 2]; Cr = data[i + 2];
k = data[i + 3]; k = data[i + 3];
CbCb = Cb * Cb; var r = -122.67195406894 +
CbCr = Cb * Cr; Cb * (-6.60635669420364e-5 * Cb + 0.000437130475926232 * Cr -
CbY = Cb * Y; 5.4080610064599e-5 * Y + 0.00048449797120281 * k -
Cbk = Cb * k; 0.154362151871126) +
CrCr = Cr * Cr; Cr * (-0.000957964378445773 * Cr + 0.000817076911346625 * Y -
Crk = Cr * k; 0.00477271405408747 * k + 1.53380253221734) +
CrY = Cr * Y; Y * (0.000961250184130688 * Y - 0.00266257332283933 * k +
YY = Y * Y; 0.48357088451265) +
Yk = Y * k; k * (-0.000336197177618394 * k + 0.484791561490776);
kk = k * k;
var r = - 122.67195406894 -
6.60635669420364e-5 * CbCb + 0.000437130475926232 * CbCr -
5.4080610064599e-5* CbY + 0.00048449797120281* Cbk -
0.154362151871126 * Cb - 0.000957964378445773 * CrCr +
0.000817076911346625 * CrY - 0.00477271405408747 * Crk +
1.53380253221734 * Cr + 0.000961250184130688 * YY -
0.00266257332283933 * Yk + 0.48357088451265 * Y -
0.000336197177618394 * kk + 0.484791561490776 * k;
var g = 107.268039397724 + var g = 107.268039397724 +
2.19927104525741e-5 * CbCb - 0.000640992018297945 * CbCr + Cb * (2.19927104525741e-5 * Cb - 0.000640992018297945 * Cr +
0.000659397001245577* CbY + 0.000426105652938837* Cbk - 0.000659397001245577 * Y + 0.000426105652938837 * k -
0.176491792462875 * Cb - 0.000778269941513683 * CrCr + 0.176491792462875) +
0.00130872261408275 * CrY + 0.000770482631801132 * Crk - Cr * (-0.000778269941513683 * Cr + 0.00130872261408275 * Y +
0.151051492775562 * Cr + 0.00126935368114843 * YY - 0.000770482631801132 * k - 0.151051492775562) +
0.00265090189010898 * Yk + 0.25802910206845 * Y - Y * (0.00126935368114843 * Y - 0.00265090189010898 * k +
0.000318913117588328 * kk - 0.213742400323665 * k; 0.25802910206845) +
k * (-0.000318913117588328 * k - 0.213742400323665);
var b = - 20.810012546947 - var b = -20.810012546947 +
0.000570115196973677 * CbCb - 2.63409051004589e-5 * CbCr + Cb * (-0.000570115196973677 * Cb - 2.63409051004589e-5 * Cr +
0.0020741088115012* CbY - 0.00288260236853442* Cbk + 0.0020741088115012 * Y - 0.00288260236853442 * k +
0.814272968359295 * Cb - 1.53496057440975e-5 * CrCr - 0.814272968359295) +
0.000132689043961446 * CrY + 0.000560833691242812 * Crk - Cr * (-1.53496057440975e-5 * Cr - 0.000132689043961446 * Y +
0.195152027534049 * Cr + 0.00174418132927582 * YY - 0.000560833691242812 * k - 0.195152027534049) +
0.00255243321439347 * Yk + 0.116935020465145 * Y - Y * (0.00174418132927582 * Y - 0.00255243321439347 * k +
0.000343531996510555 * kk + 0.24165260232407 * k; 0.116935020465145) +
k * (-0.000343531996510555 * k + 0.24165260232407);
data[offset++] = clamp0to255(r); data[offset++] = clamp0to255(r);
data[offset++] = clamp0to255(g); data[offset++] = clamp0to255(g);