How to Set the Alpha of an Uiimage in Swift Programmatically

How to set the alpha of an UIImage in SWIFT programmatically?

Luckily I was able to help myself and would like to share with you my solution:

Swift 3

// UIImage+Alpha.swift

extension UIImage {  

    func alpha(_ value:CGFloat) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        draw(at: CGPoint.zero, blendMode: .normal, alpha: value)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage!   
    }
}

The above new Swift extension I added to my project and then I changed the UIButton example as follows, to have an alpha transparent background image with a transparency of 50%.

let img = UIImage(named: "imageWithoutAlpha")!.alpha(0.5)
let myButton = UIButton()

myButton.setBackgroundImage(img, for: .normal)

How to set the opacity/alpha of a UIImage?

I just needed to do this, but thought Steven's solution would be slow. This should hopefully use graphics HW. Create a category on UIImage:

- (UIImage *)imageByApplyingAlpha:(CGFloat) alpha {
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0f);

    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGRect area = CGRectMake(0, 0, self.size.width, self.size.height);

    CGContextScaleCTM(ctx, 1, -1);
    CGContextTranslateCTM(ctx, 0, -area.size.height);

    CGContextSetBlendMode(ctx, kCGBlendModeMultiply);

    CGContextSetAlpha(ctx, alpha);

    CGContextDrawImage(ctx, area, self.CGImage);

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return newImage;
}

Change Alpha of a UIImage Programmatically

You need to change the alpha of the UIImageView it is contained in, there is no alpha property for UIImage.

Set alpha for UIView/Image

Assuming titlePicture is a UIImageView, you can edit the alpha of it directly:

cell.titlePicture.alpha = (menuItems[indexPath.row] == currentItem) ? 0.6 : 1.0

Tweak the alpha values to your liking. Example output:

alpha = 1.0:

alpha = 0.6:

Change alpha of imageview of UIButton

To conclude the comments on both other answers: subclassing and/or adding another UIImageView is the simplest choice to archieve persistent, reliant behaviour.

How to add alpha property to an UIImage set with SDWebImage?

Thanks to @Happiehappie 's comment and also this answer from another post I was able to apply the alpha property. Here is the final working code...

posterBackground.sd_setImage(with: URL(string: movieImage!), placeholderImage: UIImage(named: "poster-placeholder"), options: SDWebImageOptions(rawValue: 0), completed: { (image, error, cacheType, imageURL) in   
    self.posterBackground.image = image?.alpha(0.15)
})

how to set alpha on Backgroung image using Swift

if you want to set alpha on only background image, then re-create UIImage with changing the alpha value.

if you want to set alpha to entire button, then simply set alpha value to the button.

centerButton.alpha = 0.5

How to make one color transparent on a UIImage?

-(void)changeColor
{
    UIImage *temp23=[UIImage imageNamed:@"leaf.png"];
    CGImageRef ref1=[self createMask:temp23];
    const float colorMasking[6] = {1.0, 2.0, 1.0, 1.0, 1.0, 1.0};
    CGImageRef New=CGImageCreateWithMaskingColors(ref1, colorMasking);
    UIImage *resultedimage=[UIImage imageWithCGImage:New];
}

-(CGImageRef)createMask:(UIImage*)temp
{
    CGImageRef ref=temp.CGImage;
    int mWidth=CGImageGetWidth(ref);
    int mHeight=CGImageGetHeight(ref);
    int count=mWidth*mHeight*4;
    void *bufferdata=malloc(count);

    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

    CGContextRef cgctx = CGBitmapContextCreate (bufferdata,mWidth,mHeight, 8,mWidth*4, colorSpaceRef, kCGImageAlphaPremultipliedFirst); 

    CGRect rect = {0,0,mWidth,mHeight};
    CGContextDrawImage(cgctx, rect, ref); 
    bufferdata = CGBitmapContextGetData (cgctx);

    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, bufferdata, mWidth*mHeight*4, NULL);
    CGImageRef savedimageref = CGImageCreate(mWidth,mHeight, 8, 32, mWidth*4, colorSpaceRef, bitmapInfo,provider , NULL, NO, renderingIntent);
    CFRelease(colorSpaceRef);
    return savedimageref;
}   

The above code is tested and I changed the green color to red color by using mask

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