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QuartzDemo/QuartzRendering.m

/*

     File: QuartzRendering.m

 Abstract: Demonstrates using Quartz for drawing gradients (QuartzGradientView) and patterns (QuartzPatternView).

  Version: 3.0

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*/

#import "QuartzRendering.h"

#pragma mark - QuartzPatternView

// Colored patterns specify colors as part of their drawing

void ColoredPatternCallback(void *info, CGContextRef context)

    // Dark Blue

    CGContextSetRGBFillColor(context, 29.0 / 255.0, 156.0 / 255.0, 215.0 / 255.0, 1.00);

    CGContextFillRect(context, CGRectMake(0.0, 0.0, 8.0, 8.0));

    CGContextFillRect(context, CGRectMake(8.0, 8.0, 8.0, 8.0));

    // Light Blue

    CGContextSetRGBFillColor(context, 204.0 / 255.0, 224.0 / 255.0, 244.0 / 255.0, 1.00);

    CGContextFillRect(context, CGRectMake(8.0, 0.0, 8.0, 8.0));

    CGContextFillRect(context, CGRectMake(0.0, 8.0, 8.0, 8.0));

// Uncolored patterns take their color from the given context

void UncoloredPatternCallback(void *info, CGContextRef context)

    CGContextFillRect(context, CGRectMake(0.0, 0.0, 8.0, 8.0));

    CGContextFillRect(context, CGRectMake(8.0, 8.0, 8.0, 8.0));

@interface QuartzPatternView ()

@property (nonatomic, readonly) CGColorRef coloredPatternColor;

@property (nonatomic, readonly) CGColorSpaceRef uncoloredPatternColorSpace;

@end

@implementation QuartzPatternView

    CGColorRef _coloredPatternColor;

    CGPatternRef _uncoloredPattern;

    CGColorSpaceRef _uncoloredPatternColorSpace;

- (CGColorRef)coloredPatternColor

    if (_coloredPatternColor == NULL)

        // Colored Pattern setup

        CGPatternCallbacks coloredPatternCallbacks = {0, ColoredPatternCallback, NULL};

        // First we need to create a CGPatternRef that specifies the qualities of our pattern.

        CGPatternRef coloredPattern = CGPatternCreate(

                                                      NULL, // 'info' pointer for our callback

                                                      CGRectMake(0.0, 0.0, 16.0, 16.0), // the pattern coordinate space, drawing is clipped to this rectangle

                                                      CGAffineTransformIdentity, // a transform on the pattern coordinate space used before it is drawn.

                                                      16.0, 16.0, // the spacing (horizontal, vertical) of the pattern - how far to move after drawing each cell

                                                      kCGPatternTilingNoDistortion,

                                                      true, // this is a colored pattern, which means that you only specify an alpha value when drawing it

                                                      &coloredPatternCallbacks); // the callbacks for this pattern.

        // To draw a pattern, you need a pattern colorspace.

        // Since this is an colored pattern, the parent colorspace is NULL, indicating that it only has an alpha value.

        CGColorSpaceRef coloredPatternColorSpace = CGColorSpaceCreatePattern(NULL);

        CGFloat alpha = 1.0;

        // Since this pattern is colored, we'll create a CGColorRef for it to make drawing it easier and more efficient.

        // From here on, the colored pattern is referenced entirely via the associated CGColorRef rather than the

        // originally created CGPatternRef.

        _coloredPatternColor = CGColorCreateWithPattern(coloredPatternColorSpace, coloredPattern, &alpha);

        CGColorSpaceRelease(coloredPatternColorSpace);

        CGPatternRelease(coloredPattern);

    return _coloredPatternColor;

- (CGPatternRef)uncoloredPattern

    if (_uncoloredPattern == NULL)

        CGPatternCallbacks uncoloredPatternCallbacks = {0, UncoloredPatternCallback, NULL};

        // As above, we create a CGPatternRef that specifies the qualities of our pattern

        _uncoloredPattern = CGPatternCreate(

                                            NULL, // 'info' pointer

                                            CGRectMake(0.0, 0.0, 16.0, 16.0), // coordinate space

                                            CGAffineTransformIdentity, // transform

                                            16.0, 16.0, // spacing

                                            kCGPatternTilingNoDistortion,

                                            false, // this is an uncolored pattern, thus to draw it we need to specify both color and alpha

                                            &uncoloredPatternCallbacks); // callbacks for this pattern

    return _uncoloredPattern;

-(CGColorSpaceRef)uncoloredPatternColorSpace;

    if (_uncoloredPatternColorSpace == NULL) {

        // With an uncolored pattern we still need to create a pattern colorspace, but now we need a parent colorspace

        // We'll use the DeviceRGB colorspace here. We'll need this colorspace along with the CGPatternRef to draw this pattern later.

        CGColorSpaceRef deviceRGB = CGColorSpaceCreateDeviceRGB();

        _uncoloredPatternColorSpace = CGColorSpaceCreatePattern(deviceRGB);

        CGColorSpaceRelease(deviceRGB);

    return _uncoloredPatternColorSpace;

-(void)drawInContext:(CGContextRef)context

    // Draw the colored pattern. Since we have a CGColorRef for this pattern, we just set

    // that color current and draw.

    CGContextSetFillColorWithColor(context, self.coloredPatternColor);

    CGContextFillRect(context, CGRectMake(10.0, 10.0, 90.0, 90.0));

    // You can also stroke with a pattern.

    CGContextSetStrokeColorWithColor(context, self.coloredPatternColor);

    CGContextStrokeRectWithWidth(context, CGRectMake(120.0, 10.0, 90.0, 90.0), 8.0);

    // Since we aren't encapsulating our pattern in a CGColorRef for the uncolored pattern case, setup requires two steps.

    // First you have to set the context's current colorspace (fill or stroke) to a pattern colorspace,

    // indicating to Quartz that you want to draw a pattern.

    CGContextSetFillColorSpace(context, self.uncoloredPatternColorSpace);

    // Next you set the pattern and the color that you want the pattern to draw with.

    CGFloat color1[] = {1.0, 0.0, 0.0, 1.0};

    CGContextSetFillPattern(context, self.uncoloredPattern, color1);

    // And finally you draw!

    CGContextFillRect(context, CGRectMake(10.0, 120.0, 90.0, 90.0));

    // As long as the current colorspace is a pattern colorspace, you are free to change the pattern or pattern color

    CGFloat color2[] = {0.0, 1.0, 0.0, 1.0};

    CGContextSetFillPattern(context, self.uncoloredPattern, color2);

    CGContextFillRect(context, CGRectMake(10.0, 230.0, 90.0, 90.0));

    // And of course, just like the colored case, you can stroke with a pattern as well.

    CGContextSetStrokeColorSpace(context, self.uncoloredPatternColorSpace);

    CGContextSetStrokePattern(context, self.uncoloredPattern, color1);

    CGContextStrokeRectWithWidth(context, CGRectMake(120.0, 120.0, 90.0, 90.0), 8.0);

    // As long as the current colorspace is a pattern colorspace, you are free to change the pattern or pattern color

    CGContextSetStrokePattern(context, self.uncoloredPattern, color2);

    CGContextStrokeRectWithWidth(context, CGRectMake(120.0, 230.0, 90.0, 90.0), 8.0);

-(void)dealloc

    CGColorRelease(_coloredPatternColor);

    CGPatternRelease(_uncoloredPattern);

    CGColorSpaceRelease(_uncoloredPatternColorSpace);

@end

#pragma mark - QuartzGradientView

@interface QuartzGradientView ()

@property (nonatomic, readonly) CGGradientRef gradient;

@end

@implementation QuartzGradientView

    CGGradientRef _gradient;

-(CGGradientRef)gradient

    if(_gradient == NULL)

        CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();

        CGFloat colors[] =

            204.0 / 255.0, 224.0 / 255.0, 244.0 / 255.0, 1.00,

            29.0 / 255.0, 156.0 / 255.0, 215.0 / 255.0, 1.00,

            0.0 / 255.0,  50.0 / 255.0, 126.0 / 255.0, 1.00,

};

        _gradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, sizeof(colors)/(sizeof(colors[0])*4));

        CGColorSpaceRelease(rgb);

    return _gradient;

// Returns an appropriate starting point for the demonstration of a linear gradient

CGPoint demoLGStart(CGRect bounds)

    return CGPointMake(bounds.origin.x, bounds.origin.y + bounds.size.height * 0.25);

// Returns an appropriate ending point for the demonstration of a linear gradient

CGPoint demoLGEnd(CGRect bounds)

    return CGPointMake(bounds.origin.x, bounds.origin.y + bounds.size.height * 0.75);

// Returns the center point for for the demonstration of the radial gradient

CGPoint demoRGCenter(CGRect bounds)

    return CGPointMake(CGRectGetMidX(bounds), CGRectGetMidY(bounds));

// Returns an appropriate inner radius for the demonstration of the radial gradient

CGFloat demoRGInnerRadius(CGRect bounds)

    CGFloat r = bounds.size.width < bounds.size.height ? bounds.size.width : bounds.size.height;

    return r * 0.125;

// Returns an appropriate outer radius for the demonstration of the radial gradient

CGFloat demoRGOuterRadius(CGRect bounds)

    CGFloat r = bounds.size.width < bounds.size.height ? bounds.size.width : bounds.size.height;

    return r * 0.5;

-(CGGradientDrawingOptions)drawingOptions

    CGGradientDrawingOptions options = 0;

    if (self.extendsPastStart)

        options |= kCGGradientDrawsBeforeStartLocation;

    if (self.extendsPastEnd)

        options |= kCGGradientDrawsAfterEndLocation;

    return options;

-(void)drawInContext:(CGContextRef)context

    // Use the clip bounding box, sans a generous border

    CGRect clip = CGRectInset(CGContextGetClipBoundingBox(context), 20.0, 20.0);

    CGPoint start, end;

    CGFloat startRadius, endRadius;

    // Clip to area to draw the gradient, and draw it. Since we are clipping, we save the graphics state

    // so that we can revert to the previous larger area.

    CGContextSaveGState(context);

    CGContextClipToRect(context, clip);

    CGGradientDrawingOptions options = [self drawingOptions];

    switch(self.type)

        case kLinearGradient:

            // A linear gradient requires only a starting & ending point.

            // The colors of the gradient are linearly interpolated along the line segment connecting these two points

            // A gradient location of 0.0 means that color is expressed fully at the 'start' point

            // a location of 1.0 means that color is expressed fully at the 'end' point.

            // The gradient fills outwards perpendicular to the line segment connectiong start & end points

            // (which is why we need to clip the context, or the gradient would fill beyond where we want it to).

            // The gradient options (last) parameter determines what how to fill the clip area that is "before" and "after"

            // the line segment connecting start & end.

            start = demoLGStart(clip);

            end = demoLGEnd(clip);

            CGContextDrawLinearGradient(context, self.gradient, start, end, options);

            CGContextRestoreGState(context);

            break;

        case kRadialGradient:

            // A radial gradient requires a start & end point as well as a start & end radius.

            // Logically a radial gradient is created by linearly interpolating the center, radius and color of each

            // circle using the start and end point for the center, start and end radius for the radius, and the color ramp

            // inherant to the gradient to create a set of stroked circles that fill the area completely.

            // The gradient options specify if this interpolation continues past the start or end points as it does with

            // linear gradients.

            start = end = demoRGCenter(clip);

            startRadius = demoRGInnerRadius(clip);

            endRadius = demoRGOuterRadius(clip);

            CGContextDrawRadialGradient(context, self.gradient, start, startRadius, end, endRadius, options);

            CGContextRestoreGState(context);

            break;

    // Show the clip rect

    CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);

    CGContextStrokeRectWithWidth(context, clip, 2.0);

-(void)setType:(GradientType)newType

    if (newType != _type)

        _type = newType;

        [self setNeedsDisplay];

-(void)setExtendsPastStart:(BOOL)yn

    if (yn != _extendsPastStart)

        _extendsPastStart = yn;

        [self setNeedsDisplay];

-(void)setExtendsPastEnd:(BOOL)yn

    if (yn != _extendsPastEnd)

        _extendsPastEnd = yn;

        [self setNeedsDisplay];

-(void)dealloc

    CGGradientRelease(_gradient);

@end

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