IOS Quartz2D 通过UIColor生成图片

普通生成

示例代码：

//这里实现普通生成图片的方法
- (void)drawRect:(CGRect)rect {

    CGRect cxRect = CGRectMake(, , , );

    UIGraphicsBeginImageContextWithOptions(cxRect.size, NO, );

    [[UIColor redColor] setFill];

    UIRectFill(cxRect);

    UIImage * image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    UIImageView * imageView = [[UIImageView alloc]initWithFrame:CGRectMake(, , , )];

    imageView.image = image;

    [self addSubview:imageView];
}

效果图：

渐变颜色生成

示例代码：

//这里实现渐变颜色生成图片的方法
- (void)drawRect:(CGRect)rect {

    CGRect cxRect = CGRectMake(, , , );
    UIGraphicsBeginImageContextWithOptions(cxRect.size, NO, );
    CGContextRef context = UIGraphicsGetCurrentContext();
    UIColor * beginColor = [UIColor greenColor];
    UIColor * endColor = [UIColor redColor];
    drawLinearGradient(context, cxRect, beginColor.CGColor, endColor.CGColor);
    CGContextRestoreGState(context);

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    UIImageView * imageView = [[UIImageView alloc]initWithFrame:CGRectMake(, , , )];

    imageView.image = image;

    [self addSubview:imageView];
}

void drawLinearGradient(CGContextRef context, CGRect rect, CGColorRef startColor, CGColorRef endColor)
{
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGFloat locations[] = { 0.0, 1.0 };

    NSArray *colors = @[(__bridge id) startColor, (__bridge id) endColor];

    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);
    CGPoint startPoint = CGPointMake(rect.size.width/, );
    CGPoint endPoint = CGPointMake(rect.size.width/, rect.size.height/1.5);

    CGContextSaveGState(context);
    CGContextAddRect(context, rect);
    CGContextClip(context);
    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, );
    CGContextSetStrokeColorWithColor(context, [[UIColor clearColor] CGColor]);
}

效果图：