Gradient Color Image

UIImage+colorImage.h

//
//  UIImage+colorImage.h
//  HappyMan
//
//  Created by Arthur on 2015/6/24.
//  Copyright (c) 2015年 LW. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIImage (colorImage)

+ (UIImage *)imageWithColor:(UIColor *)color;

+ (UIImage *)imageVerticalGradientWithSize:(CGSize)size colorset:(NSArray*)colors locations:(CGFloat[])locations;

+ (UIImage *)imageHorizontalGradientWithSize:(CGSize)size colorset:(NSArray*)colors locations:(CGFloat[])locations;

+ (UIImage *)shadowImage;

@end

UIImage+colorImage.m

//
//  UIImage+colorImage.m
//  HappyMan
//
//  Created by Arthur on 2015/6/24.
//  Copyright (c) 2015年 LW. All rights reserved.
//

#import "UIImage+colorImage.h"

@implementation UIImage (colorImage)

+ (UIImage *)imageWithColor:(UIColor *)color
{
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
	
    CGContextSetFillColorWithColor(context, color.CGColor);
    CGContextFillRect(context, rect);
	
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
	
    return image;
}

+ (UIImage *)imageVerticalGradientWithSize:(CGSize)size colorset:(NSArray*)colors locations:(CGFloat[])locations
{
    UIGraphicsBeginImageContext(size);
	
    // 建立一個 RGB 的顏色空間
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = UIGraphicsGetCurrentContext();
	
	NSMutableArray *gradientColors = [NSMutableArray array];;
	for (UIColor *color in colors) {
		if ([color isKindOfClass:[UIColor class]]) {
			[gradientColors addObject:(id)color.CGColor];
		}
	}
	CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)gradientColors, locations);
	
    // 建立漸層的起點與終點
    CGPoint beginPoint = CGPointMake(size.width / 2, 0);
    CGPoint endPoint = CGPointMake(size.width / 2, size.height);
	
    CGContextDrawLinearGradient(context, gradient, beginPoint, endPoint, 0);
	CGContextSaveGState(context);
	
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
	
    // 結束 context，並且釋放記憶體
    UIGraphicsEndImageContext();
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(gradient);
	
	return image;
}

+(UIImage *)imageHorizontalGradientWithSize:(CGSize)size colorset:(NSArray *)colors locations:(CGFloat [])locations
{
    UIGraphicsBeginImageContext(size);
	
    // 建立一個 RGB 的顏色空間
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = UIGraphicsGetCurrentContext();
	
	NSMutableArray *gradientColors = [NSMutableArray array];;
	for (UIColor *color in colors) {
		if ([color isKindOfClass:[UIColor class]]) {
			[gradientColors addObject:(id)color.CGColor];
		}
	}
	CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)gradientColors, locations);
	
    // 建立漸層的起點與終點
    CGPoint beginPoint = CGPointMake(0, size.height / 2);
    CGPoint endPoint = CGPointMake(size.width, size.height / 2);
	
    CGContextDrawLinearGradient(context, gradient, beginPoint, endPoint, 0);
	CGContextSaveGState(context);
	
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
	
    // 結束 context，並且釋放記憶體
    UIGraphicsEndImageContext();
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(gradient);
	
	return image;
}

+(UIImage *)shadowImage
{
	NSArray *colors = @[[UIColor colorWithWhite:0 alpha:0.4], [UIColor colorWithWhite:0 alpha:0]];
	CGFloat locations[] = {0, 1};
	return [UIImage imageVerticalGradientWithSize:CGSizeMake([UIScreen mainScreen].bounds.size.width, 1) colorset:colors locations:locations];
}

@end

ViewController.h

//
//  ViewController.h
//  HappyTest7
//
//  Created by Jason on 2015/9/11.
//  Copyright (c) 2015年 HT. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
{
    IBOutlet UIImageView *myImageView;
    IBOutlet UIImageView *myImageView2;
    IBOutlet UIImageView *myImageView3;
}

@end

ViewController.m

//
//  ViewController.m
//  HappyTest7
//
//  Created by Jason on 2015/9/11.
//  Copyright (c) 2015年 HT. All rights reserved.
//

#import "ViewController.h"
#import "UIImage+colorImage.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSArray *colors = @[[UIColor colorWithWhite:0 alpha:1], [UIColor colorWithWhite:0 alpha:0.8], [UIColor colorWithWhite:0 alpha:0.2], [UIColor colorWithWhite:0 alpha:0.1]];
    CGFloat locations[] = {0, 0.2, 0.8, 1};
    
    // 產生垂直漸層影像
    UIImage *darkImage = [UIImage imageVerticalGradientWithSize:myImageView3.bounds.size colorset:colors locations:locations];
    [myImageView3 setImage:darkImage];

    // 產生水平漸層影像
    darkImage = [UIImage imageHorizontalGradientWithSize:myImageView2.bounds.size colorset:colors locations:locations];
    [myImageView2 setImage:darkImage];

    // 產生單純影像
    darkImage = [UIImage imageWithColor:[UIColor blueColor]];
    [myImageView setImage:darkImage];

}

@end