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//
// GTMLinearRGBShading.m
//
// Copyright 2006-2008 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//
#import "GTMLinearRGBShading.h"
#import "GTMDefines.h"
// Carbon callback function required for CoreGraphics
static void cShadeFunction(void *info, const CGFloat *inPos, CGFloat *outVals);
@implementation GTMLinearRGBShading
+ (id)shadingFromColor:(NSColor *)begin toColor:(NSColor *)end
fromSpaceNamed:(NSString*)colorSpaceName {
NSColor *theColors[] = { begin, end };
CGFloat thePositions[] = { 0.0, 1.0 };
return [[self class] shadingWithColors:theColors
fromSpaceNamed:colorSpaceName
atPositions:thePositions
count:(sizeof(thePositions)/sizeof(CGFloat))];
}
+ (id)shadingWithColors:(NSColor **)colors fromSpaceNamed:(NSString*)colorSpaceName
atPositions:(CGFloat *)positions count:(NSUInteger)count {
GTMLinearRGBShading *theShading = [[[self alloc] initWithColorSpaceName:colorSpaceName] autorelease];
for (NSUInteger i = 0; i < count; ++i) {
[theShading insertStop:colors[i] atPosition:positions[i]];
}
return theShading;
}
- (id)initWithColorSpaceName:(NSString*)colorSpaceName {
if ((self = [super init])) {
if ([colorSpaceName isEqualToString:NSDeviceRGBColorSpace]) {
isCalibrated_ = NO;
} else if ([colorSpaceName isEqualToString:NSCalibratedRGBColorSpace]) {
isCalibrated_ = YES;
}
else {
[self release];
self = nil;
}
}
return self;
}
- (void)dealloc {
if (nil != function_) {
CGFunctionRelease(function_);
}
if (nil != colorSpace_) {
CGColorSpaceRelease(colorSpace_);
}
[super dealloc];
}
- (void)insertStop:(id)item atPosition:(CGFloat)position {
NSString *colorSpaceName = isCalibrated_ ? NSCalibratedRGBColorSpace : NSDeviceRGBColorSpace;
NSColor *tempColor = [item colorUsingColorSpaceName: colorSpaceName];
if (nil != tempColor) {
[super insertStop:tempColor atPosition:position];
}
}
// Calculate a linear value based on our stops
- (id)valueAtPosition:(CGFloat)position {
NSUInteger positionIndex = 0;
NSUInteger colorCount = [self stopCount];
CGFloat stop1Position = 0.0;
NSColor *stop1Color = [self stopAtIndex:positionIndex position:&stop1Position];
positionIndex += 1;
CGFloat stop2Position = 0.0;
NSColor *stop2Color = nil;
if (colorCount > 1) {
stop2Color = [self stopAtIndex:positionIndex position:&stop2Position];
positionIndex += 1;
} else {
// if we only have one value, that's what we return
stop2Position = stop1Position;
stop2Color = stop1Color;
}
while (positionIndex < colorCount && stop2Position < position) {
stop1Color = stop2Color;
stop1Position = stop2Position;
stop2Color = [self stopAtIndex:positionIndex position:&stop2Position];
positionIndex += 1;
}
if (position <= stop1Position) {
// if we are less than our lowest position, return our first color
[stop1Color getRed:&colorValue_[0] green:&colorValue_[1]
blue:&colorValue_[2] alpha:&colorValue_[3]];
} else if (position >= stop2Position) {
// likewise if we are greater than our highest position, return the last color
[stop2Color getRed:&colorValue_[0] green:&colorValue_[1]
blue:&colorValue_[2] alpha:&colorValue_[3]];
} else {
// otherwise interpolate between the two
position = (position - stop1Position) / (stop2Position - stop1Position);
CGFloat red1, red2, green1, green2, blue1, blue2, alpha1, alpha2;
[stop1Color getRed:&red1 green:&green1 blue:&blue1 alpha:&alpha1];
[stop2Color getRed:&red2 green:&green2 blue:&blue2 alpha:&alpha2];
colorValue_[0] = (red2 - red1) * position + red1;
colorValue_[1] = (green2 - green1) * position + green1;
colorValue_[2] = (blue2 - blue1) * position + blue1;
colorValue_[3] = (alpha2 - alpha1) * position + alpha1;
}
// Yes, I am casting a CGFloat[] to an id to pass it by the compiler. This
// significantly improves performance though as I avoid creating an NSColor
// for every scanline which later has to be cleaned up in an autorelease pool
// somewhere. Causes guardmalloc to run significantly faster.
return (id)colorValue_;
}
//
// switch from C to obj-C. The callback to a shader is a c function
// but we want to call our objective c object to do all the
// calculations for us. We have passed our function our
// GTMLinearRGBShading as an obj-c object in the |info| so
// we just turn around and ask it to calculate our value based
// on |inPos| and then stick the results back in |outVals|
//
// Args:
// info: is the GTMLinearRGBShading as an
// obj-C object.
// inPos: the position to calculate values for. This is a pointer to
// a single float value
// outVals: where we store our return values. Since we are calculating
// an RGBA color, this is a pointer to an array of four float values
// ranging from 0.0 to 1.0
//
//
static void cShadeFunction(void *info, const CGFloat *inPos, CGFloat *outVals) {
id object = (id)info;
CGFloat *colorValue = (CGFloat*)[object valueAtPosition:*inPos];
outVals[0] = colorValue[0];
outVals[1] = colorValue[1];
outVals[2] = colorValue[2];
outVals[3] = colorValue[3];
}
- (CGFunctionRef) shadeFunction {
// lazily create the function as necessary
if (nil == function_) {
// We have to go to carbon here, and create the CGFunction. Note that this
// diposed if necessary in the dealloc call.
const CGFunctionCallbacks shadeFunctionCallbacks = { 0, &cShadeFunction, NULL };
// TODO: this code assumes that we have a range from 0.0 to 1.0
// which may not be true according to the stops that the user has given us.
// In general you have stops at 0.0 and 1.0, so this will do for right now
// but may be an issue in the future.
const CGFloat inRange[2] = { 0.0, 1.0 };
const CGFloat outRange[8] = { 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0 };
function_ = CGFunctionCreate(self,
sizeof(inRange) / (sizeof(CGFloat) * 2), inRange,
sizeof(outRange) / (sizeof(CGFloat) * 2), outRange,
&shadeFunctionCallbacks);
}
return function_;
}
- (CGColorSpaceRef)colorSpace {
// lazily create the colorspace as necessary
if (nil == colorSpace_) {
if (isCalibrated_) {
colorSpace_ = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
} else {
colorSpace_ = CGColorSpaceCreateDeviceRGB();
}
}
return colorSpace_;
}
@end
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