Invert Filter has been added

Test case added in the preset options

Classes/ImageFilter.h

@@ -30,6 +30,7 @@ typedef NSUInteger CurveChannel;
 - (UIImage*) opacity:(double)amount;
 - (UIImage*) contrast:(double)amount;
 - (UIImage*) bias:(double)amount;
+- (UIImage*) invert;
 
 /* Color Correction */
 - (UIImage*) levels:(NSInteger)black mid:(NSInteger)mid white:(NSInteger)white;

Classes/ImageFilter.m

@@ -208,6 +208,21 @@ void filterBias(UInt8 *pixelBuf, UInt32 offset, void *context)
 	pixelBuf[b] = SAFECOLOR((blue * calcBias(((double)blue / 255.0f), val)));
 }
 
+void filterInvert(UInt8 *pixelBuf, UInt32 offset, void *context)
+{	
+	int r = offset;
+	int g = offset+1;
+	int b = offset+2;
+
+	int red = pixelBuf[r];
+	int green = pixelBuf[g];
+	int blue = pixelBuf[b];
+
+	pixelBuf[r] = SAFECOLOR(255-red);
+	pixelBuf[g] = SAFECOLOR(255-green);
+	pixelBuf[b] = SAFECOLOR(255-blue);
+}
+
 #pragma mark Filters
 -(UIImage*)greyscale 
 {
@@ -254,6 +269,11 @@ - (UIImage*)bias:(double)amount
 	return [self applyFilter:filterBias context:&amount];	
 }
 
+- (UIImage*)invert
+{
+	return [self applyFilter:filterInvert context:nil];
+}
+
 #pragma mark -
 #pragma mark Blends
 #pragma mark Internals

Classes/iphone_filtersViewController.h

@@ -17,6 +17,7 @@ typedef enum
 	FilterBrightness,
 	FilterContrast,
 	FilterGamma,
+    FilterInvert,
 	FilterTotal
 } FilterOptions;
 

Classes/iphone_filtersViewController.m

@@ -72,6 +72,7 @@ - (IBAction) buttonPackagedClicked:(id)sender
 									NSLocalizedString(@"Lomo",@""),
 									NSLocalizedString(@"Vignette",@""),
 									NSLocalizedString(@"Polaroidish",@""),
+									NSLocalizedString(@"Invert",@""),
 									nil] autorelease];
 	self.actionSheetPackaged.actionSheetStyle = UIActionSheetStyleDefault;
 	[self.actionSheetPackaged showInView:self.view]; // show from our table view (pops up in the middle of the table)	
@@ -115,6 +116,7 @@ - (IBAction) sliderMoved:(id)sender
 	ActionSheetPackagedOptionLomo,
 	ActionSheetPackagedOptionVignette,
 	ActionSheetPackagedOptionPolaroidish,
+    ActionSheetPackagedOptionInvert,
 	ActionSheetPackagedOptionTotal
 } ActionSheetPackagedOptions;
 
@@ -148,6 +150,9 @@ - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger
 			case ActionSheetPackagedOptionPolaroidish:
 				self.imageView.image = [image polaroidish];
 				break;
+			case ActionSheetPackagedOptionInvert:
+				self.imageView.image = [image invert];
+				break;                
 			default:
 				break;
 		}