Added the drawing code

jernejstrasner · Nov 8, 2013 · 3b61c29 · 3b61c29
1 parent f00bb63
commit 3b61c29
Showing 1 changed file with 74 additions and 1 deletion.
diff --git a/SmoothGradient/JSTGradientView.m b/SmoothGradient/JSTGradientView.m
@@ -20,7 +20,80 @@ - (void)redrawSmooth:(BOOL)smooth
 
 - (void)drawRect:(CGRect)rect
 {
-
+	// Draw the gradient background
+	CGContextRef context = UIGraphicsGetCurrentContext();
+	CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
+
+	if (_smooth) {
+		// Define the shading callbacks
+		CGFunctionCallbacks callbacks = {0, blackShade, NULL};
+
+		// As input to our function we want 1 value in the range [0.0, 1.0].
+		// This is our position within the 'gradient'.
+		size_t domainDimension = 1;
+		CGFloat domain[2] = {0.0f, 1.0f};
+
+		// The output of our function is 2 values, each in the range [0.0, 1.0].
+		// This is our selected color for the input position.
+		// The 2 values are the white and alpha components.
+		size_t rangeDimension = 2;
+		CGFloat range[8] = {0.0f, 1.0f, 0.0f, 1.0f};
+
+		// Create the shading finction
+		CGFunctionRef function = CGFunctionCreate(NULL, domainDimension, domain, rangeDimension, range, &callbacks);
+
+		// Create the shading object
+		CGShadingRef shading = CGShadingCreateAxial(colorSpace, CGPointMake(1, rect.size.height), CGPointMake(1, rect.size.height*0.75f), function, YES, YES);
+
+		// Draw the shading
+		CGContextDrawShading(context, shading);
+
+		// Clean up
+		CGFunctionRelease(function);
+		CGShadingRelease(shading);
+	}
+	else {
+		// Color components
+		CGFloat colorComponents[4] = {
+			0.0f, 0.5f,
+			0.0f, 0.0f
+		};
+
+		// Color locations
+		CGFloat locations[2] = {
+			0.0f,
+			1.0f
+		};
+
+		// The gradient
+		CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace, colorComponents, locations, 2);
+
+		// Draw the gradient
+		CGContextDrawLinearGradient(context, gradient, CGPointMake(1, rect.size.height), CGPointMake(1, rect.size.height*0.75f), kCGGradientDrawsAfterEndLocation | kCGGradientDrawsBeforeStartLocation);
+
+		// Clean up
+		CGGradientRelease(gradient);
+	}
+
+	// Clean up
+	CGColorSpaceRelease(colorSpace);
+}
+
+// This is the callback of our shading function.
+// info:    not needed
+// inData:  contains a single float that gives is the current position within the gradient
+// outData: we fill this with the color to display at the given position
+static void blackShade(void *info, const CGFloat *inData, CGFloat *outData)
+{
+	float p = inData[0];
+	outData[0] = 0.0f;
+	outData[1] = (1.0f-slope(p, 2.0f)) * 0.5f;
+}
+
+// Distributes values on a slope aka. ease-in ease-out
+static float slope(float x, float A) {
+	float p = powf(x, A);
+	return p/(p + powf(1.0f-x, A));
 }
 
 @end