UIImage具有渐变效果

最新推荐文章于 2018-04-23 08:07:07 发布

zxc110110

最新推荐文章于 2018-04-23 08:07:07 发布

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分类专栏： UI 文章标签： image components c layer null

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本文介绍了一个UIImage的Category实现方法，该方法可以为图片添加背景颜色，并应用渐变及阴影效果。通过设置不同的参数，如渐变透明度、阴影颜色等，可以轻松地创建美观的图片效果。

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做一个UIImage的category，直接上代码：
- (UIImage *) imageWithBackgroundColor

:(UIColor *)bgColor
                          shadeAlpha1:(CGFloat)alpha1
                          shadeAlpha2:(CGFloat)alpha2
                          shadeAlpha3:(CGFloat)alpha3
                          shadowColor:(UIColor *)shadowColor
                         shadowOffset:(CGSize)shadowOffset
                           shadowBlur:(CGFloat)shadowBlur {
    UIImage*image = self;
    CGColorRefcgColor = [bgColor CGColor];
    CGColorRefcgShadowColor = [shadowColor CGColor];
    CGFloatcomponents[16] ={1,1,1,alpha1,1,1,1,alpha1,1,1,1,alpha2,1,1,1,alpha3};
    CGFloatlocations[4] = {0,0.5,0.6,1};
   CGColorSpaceRef colorSpace =CGColorSpaceCreateDeviceRGB();
   CGGradientRef colorGradient =CGGradientCreateWithColorComponents(colorSpace, components,locations, (size_t)4);
    CGRectcontextRect;
   contextRect.origin.x = 0.0f;
   contextRect.origin.y = 0.0f;
   contextRect.size = [image size];
   //contextRect.size = CGSizeMake([image size].width+5,[imagesize].height+5);
    // Retrievesource image and begin image context
    UIImage*itemImage = image;
    CGSizeitemImageSize = [itemImage size];
    CGPointitemImagePosition;
   itemImagePosition.x = ceilf((contextRect.size.width -itemImageSize.width) / 2);
   itemImagePosition.y = ceilf((contextRect.size.height -itemImageSize.height) / 2);
   UIGraphicsBeginImageContext(contextRect.size);
    CGContextRefc = UIGraphicsGetCurrentContext();
    // Setupshadow
   CGContextSetShadowWithColor(c, shadowOffset, shadowBlur,cgShadowColor);
    // Setuptransparency layer and clip to mask
   CGContextBeginTransparencyLayer(c, NULL);
   CGContextScaleCTM(c, 1.0, -1.0);
   CGContextClipToMask(c, CGRectMake(itemImagePosition.x,-itemImagePosition.y, itemImageSize.width, -itemImageSize.height),[itemImage CGImage]);
    // Fill andend the transparency layer
   CGContextSetFillColorWithColor(c,cgColor);
   contextRect.size.height = -contextRect.size.height;
   CGContextFillRect(c, contextRect);
   CGContextDrawLinearGradient(c,colorGradient,CGPointZero,CGPointMake(contextRect.size.width*1.0/4.0,contextRect.size.height),0);
   CGContextEndTransparencyLayer(c);
   //CGPointMake(contextRect.size.width*3.0/4.0, 0)
    // Setselected image and end context
    UIImage*resultImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();
   CGColorSpaceRelease(colorSpace);
   CGGradientRelease(colorGradient);
    returnresultImage;
}

用法如下

UIImage *niceImage = [[UIImage imageNamed:@"image_name"]imageWithBackgroundColor:[UIColor colorWithRed:41.0/255.0green:147.0/255.0 blue:239.0/255.0 alpha:1.0]
                                                                     shadeAlpha1:0.6
                                                                     shadeAlpha2:0.0
                                                                     shadeAlpha3:0.4
                                                                     shadowColor:[UIColor blackColor]
                                                                    shadowOffset:CGSizeMake(0.0f, -1.0f)