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Implement initial CalGray support

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Gamma and Whitepoint are supported in this patch for CalGray.
Blackpoint is not supported.
This commit is contained in:
Kalervo Kujala 2013-04-25 22:26:42 +03:00
parent b9bceb4c4b
commit a5bf02573d
3 changed files with 675 additions and 2 deletions
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118
src/shared/colorspace.js
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@ -15,7 +15,7 @@
* limitations under the License.
*/
/* globals error, info, isArray, isDict, isName, isStream, isString,
PDFFunction, warn, shadow */
PDFFunction, warn, shadow, TODO */
'use strict';
@ -132,6 +132,11 @@ var ColorSpace = (function ColorSpaceClosure() {
return this.singletons.rgb;
case 'DeviceCmykCS':
return this.singletons.cmyk;
case 'CalGrayCS':
var whitePoint = IR[1].WhitePoint;
var blackPoint = IR[1].BlackPoint;
var gamma = IR[1].Gamma;
return new CalGrayCS(whitePoint, blackPoint, gamma);
case 'PatternCS':
var basePatternCS = IR[1];
if (basePatternCS)
@ -207,7 +212,8 @@ var ColorSpace = (function ColorSpaceClosure() {
case 'CMYK':
return 'DeviceCmykCS';
case 'CalGray':
return 'DeviceGrayCS';
var params = cs[1].getAll();
return ['CalGrayCS', params];
case 'CalRGB':
return 'DeviceRgbCS';
case 'ICCBased':
@ -627,6 +633,113 @@ var DeviceCmykCS = (function DeviceCmykCSClosure() {
return DeviceCmykCS;
})();
//
// CalGrayCS: Based on "PDF Reference, Sixth Ed", p.245
//
var CalGrayCS = (function CalGrayCSClosure() {
function CalGrayCS(whitePoint, blackPoint, gamma) {
this.name = 'CalGray';
this.numComps = 3;
this.defaultColor = new Float32Array([0, 0, 0]);
if (!whitePoint) {
error('WhitePoint missing - required for color space CalGray');
}
blackPoint = blackPoint || [0, 0, 0];
gamma = gamma || 1;
// Translate arguments to spec variables.
this.XW = whitePoint[0];
this.YW = whitePoint[1];
this.ZW = whitePoint[2];
this.XB = blackPoint[0];
this.YB = blackPoint[1];
this.ZB = blackPoint[2];
this.G = gamma;
// Validate variables as per spec.
if (this.XW < 0 || this.ZW < 0 || this.YW !== 1) {
error('Invalid WhitePoint components for ' + this.name +
', no fallback available');
}
if (this.XB < 0 || this.YB < 0 || this.ZB < 0) {
info('Invalid BlackPoint for ' + this.name + ', falling back to default');
this.XB = this.YB = this.ZB = 0;
}
if (this.XB !== 0 || this.YB !== 0 || this.ZB !== 0) {
TODO(this.name + ', BlackPoint: XB: ' + this.XB + ', YB: ' + this.YB +
', ZB: ' + this.ZB + ', only default values are supported.');
}
if (this.G < 1) {
info('Invalid Gamma: ' + this.G + ' for ' + this.name +
', falling back to default');
this.G = 1;
}
}
CalGrayCS.prototype = {
getRgb: function CalGrayCS_getRgb(src, srcOffset) {
var rgb = new Uint8Array(3);
this.getRgbItem(src, srcOffset, rgb, 0);
return rgb;
},
getRgbItem: function CalGrayCS_getRgbItem(src, srcOffset,
dest, destOffset) {
// A represents a gray component of a calibrated gray space.
// A <---> AG in the spec
var A = src[srcOffset];
var AG = Math.pow(A, this.G);
// Computes intermediate variables M, L, N as per spec.
// Except if other than default BlackPoint values are used.
var M = this.XW * AG;
var L = this.YW * AG;
var N = this.ZW * AG;
// Decode XYZ, as per spec.
var X = M;
var Y = L;
var Z = N;
// http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html, Ch 4.
// This yields values in range [0, 100].
var Lstar = Math.max(116 * Math.pow(Y, 1 / 3) - 16, 0);
// Convert values to rgb range [0, 255].
dest[destOffset] = Lstar * 255 / 100;
dest[destOffset + 1] = Lstar * 255 / 100;
dest[destOffset + 2] = Lstar * 255 / 100;
},
getRgbBuffer: function CalGrayCS_getRgbBuffer(src, srcOffset, count,
dest, destOffset, bits) {
// TODO: This part is copied from DeviceGray. Make this utility function.
var scale = 255 / ((1 << bits) - 1);
var j = srcOffset, q = destOffset;
for (var i = 0; i < count; ++i) {
var c = (scale * src[j++]) | 0;
dest[q++] = c;
dest[q++] = c;
dest[q++] = c;
}
},
getOutputLength: function CalGrayCS_getOutputLength(inputLength) {
return inputLength * 3;
},
isPassthrough: ColorSpace.prototype.isPassthrough,
createRgbBuffer: ColorSpace.prototype.createRgbBuffer,
isDefaultDecode: function CalGrayCS_isDefaultDecode(decodeMap) {
return ColorSpace.isDefaultDecode(decodeMap, this.numComps);
},
usesZeroToOneRange: true
};
return CalGrayCS;
})();
//
// LabCS: Based on "PDF Reference, Sixth Ed", p.250
//
@ -767,3 +880,4 @@ var LabCS = (function LabCSClosure() {
};
return LabCS;
})();