I would like my UIView to fade from 100% opacity to 0% opacity. Any thoughts on how I can do this?
Ray Wenderlich has a great tutorial on setting gradients for objects. My suggestion is to modify the following code to suit your needs.
//Ray's code:
void drawLinearGradient(CGContextRef context, CGRect rect, CGColorRef startColor,
CGColorRef endColor) {
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = { 0.0, 1.0 };
NSArray *colors = [NSArray arrayWithObjects:(id)startColor, (id)endColor, nil];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace,
(CFArrayRef) colors, locations);
CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect));
CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect));
CGContextSaveGState(context);
CGContextAddRect(context, rect);
CGContextClip(context);
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGContextRestoreGState(context);
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
If the view, together with its labels, is sitting on some static background image or color, a quick and dirty trick is to create gradient PNGs of that image or color and place them over the view.
Otherwise, see if you can adapt this CALayer gradient mask solution for your view.
I need to darken a UIImageView when it gets touched, almost exactly like icons on the springboard (home screen).
Should I be added UIView with a 0.5 alpha and black background. This seems clumsy. Should I be using Layers or something (CALayers).
I would let a UIImageView handle the actual drawing of the image, but toggle the image to one that's been darkened in advance. Here's some code I've used to generate darkened images with alpha maintained:
+ (UIImage *)darkenImage:(UIImage *)image toLevel:(CGFloat)level
{
// Create a temporary view to act as a darkening layer
CGRect frame = CGRectMake(0.0, 0.0, image.size.width, image.size.height);
UIView *tempView = [[UIView alloc] initWithFrame:frame];
tempView.backgroundColor = [UIColor blackColor];
tempView.alpha = level;
// Draw the image into a new graphics context
UIGraphicsBeginImageContext(frame.size);
CGContextRef context = UIGraphicsGetCurrentContext();
[image drawInRect:frame];
// Flip the context vertically so we can draw the dark layer via a mask that
// aligns with the image's alpha pixels (Quartz uses flipped coordinates)
CGContextTranslateCTM(context, 0, frame.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextClipToMask(context, frame, image.CGImage);
[tempView.layer renderInContext:context];
// Produce a new image from this context
CGImageRef imageRef = CGBitmapContextCreateImage(context);
UIImage *toReturn = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
UIGraphicsEndImageContext();
[tempView release];
return toReturn;
}
How about subclassing UIView and adding a UIImage ivar (called image)? Then you could override -drawRect: something like this, provided you had a boolean ivar called pressed that was set while touched.
- (void)drawRect:(CGRect)rect
{
[image drawAtPoint:(CGPointMake(0.0, 0.0))];
// if pressed, fill rect with dark translucent color
if (pressed)
{
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSaveGState(ctx);
CGContextSetRGBFillColor(ctx, 0.5, 0.5, 0.5, 0.5);
CGContextFillRect(ctx, rect);
CGContextRestoreGState(ctx);
}
}
You would want to experiment with RGBA values above. And, of course, non-rectangular shapes would require a bit more work - like a CGMutablePathRef.
UIImageView can have multiple images; you could have two versions of the image and switch to the darker one when needed.
I know it's possible to tint a rectangular image by drawing a CGContextFillRect over it and setting the blend mode. However, I can't figure out how to do a tint on a transparent image such as an icon. It must be possible since the SDK does it itself on tab-bars in such. Would anyone be able to provide a snippet?
UPDATE:
Lots of great suggestions have been given for this problem since I originally asked. Be sure to read through all the answers to figure out what suits you best.
UPDATE (Apr 30, 2015):
With iOS 7.0, I can now just do the following, which would satisfy the needs of my original question. But if you have more complicated cases, check out all the answers.
UIImage *iconImage = [[UIImage imageNamed:#"myImageName"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
UIImageView *icon = [[UIImageView alloc] initWithImage:iconImage];
icon.tintColor = [UIColor redColor];
Update: Here is a Gist for a Swift UIColor extension using the code below.
If you have a greyscale image and want white become the tinting color, kCGBlendModeMultiply is the way to go. With this method, you cannot have highlights lighter than your tinting color.
On the contrary, if you have either a non-greyscale image, OR you have highlights and shadows that should be preserved, the blend mode kCGBlendModeColor is the way to go. White will stay white and black will stay black as the lightness of the image is preserved. This mode is just made for tinting - it is the same as Photoshop's Color layer blend mode (disclaimer: slightly differing results may happen).
Note that tinting alpha-pixels does not work correctly neither in iOS nor in Photoshop - half-transparent black pixels would not stay black. I updated the answer below to work around that issue, it took quite a long time to find out.
You can also use one of the blend modes kCGBlendModeSourceIn/DestinationIn instead of CGContextClipToMask.
If you want to create a UIImage, each of the following code sections can be surrounded by the following code:
UIGraphicsBeginImageContextWithOptions (myIconImage.size, NO, myIconImage.scale); // for correct resolution on retina, thanks #MobileVet
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0, myIconImage.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGRect rect = CGRectMake(0, 0, myIconImage.size.width, myIconImage.size.height);
// image drawing code here
UIImage *coloredImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
So here's the code for tinting a transparent image with kCGBlendModeColor:
// draw black background to preserve color of transparent pixels
CGContextSetBlendMode(context, kCGBlendModeNormal);
[[UIColor blackColor] setFill];
CGContextFillRect(context, rect);
// draw original image
CGContextSetBlendMode(context, kCGBlendModeNormal);
CGContextDrawImage(context, rect, myIconImage.CGImage);
// tint image (loosing alpha) - the luminosity of the original image is preserved
CGContextSetBlendMode(context, kCGBlendModeColor);
[tintColor setFill];
CGContextFillRect(context, rect);
// mask by alpha values of original image
CGContextSetBlendMode(context, kCGBlendModeDestinationIn);
CGContextDrawImage(context, rect, myIconImage.CGImage);
If your image has no half-transparent pixels, you could also do it the other way around with kCGBlendModeLuminosity:
// draw tint color
CGContextSetBlendMode(context, kCGBlendModeNormal);
[tintColor setFill];
CGContextFillRect(context, rect);
// replace luminosity of background (ignoring alpha)
CGContextSetBlendMode(context, kCGBlendModeLuminosity);
CGContextDrawImage(context, rect, myIconImage.CGImage);
// mask by alpha values of original image
CGContextSetBlendMode(context, kCGBlendModeDestinationIn);
CGContextDrawImage(context, rect, myIconImage.CGImage);
If you don't care for luminosity, as you just have got an image with an alpha channel that should be tinted with a color, you can do it in a more efficient way:
// draw tint color
CGContextSetBlendMode(context, kCGBlendModeNormal);
[tintColor setFill];
CGContextFillRect(context, rect);
// mask by alpha values of original image
CGContextSetBlendMode(context, kCGBlendModeDestinationIn);
CGContextDrawImage(context, rect, myIconImage.CGImage);
or the other way around:
// draw alpha-mask
CGContextSetBlendMode(context, kCGBlendModeNormal);
CGContextDrawImage(context, rect, myIconImage.CGImage);
// draw tint color, preserving alpha values of original image
CGContextSetBlendMode(context, kCGBlendModeSourceIn);
[tintColor setFill];
CGContextFillRect(context, rect);
Have fun!
I had most success with this method, because the others I tried caused distorted colors for semi-transparent pixels for certain color-combinations. This should also be a bit better on the performance side.
+ (UIImage *) imageNamed:(NSString *) name withTintColor: (UIColor *) tintColor {
UIImage *baseImage = [UIImage imageNamed:name];
CGRect drawRect = CGRectMake(0, 0, baseImage.size.width, baseImage.size.height);
UIGraphicsBeginImageContextWithOptions(baseImage.size, NO, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0, baseImage.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// draw original image
CGContextSetBlendMode(context, kCGBlendModeNormal);
CGContextDrawImage(context, drawRect, baseImage.CGImage);
// draw color atop
CGContextSetFillColorWithColor(context, tintColor.CGColor);
CGContextSetBlendMode(context, kCGBlendModeSourceAtop);
CGContextFillRect(context, drawRect);
UIImage *tintedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return tintedImage;
}
After searching around, the best solution I've come to thus far is to use a combination of blend mode and the clipping mask to achieve colorizing/tinting a transparent PNG:
CGContextSetBlendMode (context, kCGBlendModeMultiply);
CGContextDrawImage(context, rect, myIconImage.CGImage);
CGContextClipToMask(context, rect, myIconImage.CGImage);
CGContextSetFillColorWithColor(context, tintColor);
CGContextFillRect(context, rect);
I can get results very close to the tint in the Apple navigation bar by using kCGBlendModeOverlay. Taking excelent #fabb answer and combining #omz approach in this post https://stackoverflow.com/a/4684876/229019 I came with this solution that helds the results I was expecting:
- (UIImage *)tintedImageUsingColor:(UIColor *)tintColor;
{
UIGraphicsBeginImageContextWithOptions (self.size, NO, [[UIScreen mainScreen] scale]);
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
// draw original image
[self drawInRect:rect blendMode:kCGBlendModeNormal alpha:1.0f];
// tint image (loosing alpha).
// kCGBlendModeOverlay is the closest I was able to match the
// actual process used by apple in navigation bar
CGContextSetBlendMode(context, kCGBlendModeOverlay);
[tintColor setFill];
CGContextFillRect(context, rect);
// mask by alpha values of original image
[self drawInRect:rect blendMode:kCGBlendModeDestinationIn alpha:1.0f];
UIImage *tintedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return tintedImage;
}
Here's an example tinting several grayscale images with transparency:
:
The first line is the apple toolbar tinted [UIColor orangeColor].
The second line is the same gradient tinted in several colors starting with clear color (= the actual gradient) and ending with the same orange.
The third is a simple circle with transparency (the linen is the background color)
The forth line is a complex dark noisy texture
You could create an UIImage category and do it like this:
- (instancetype)tintedImageWithColor:(UIColor *)tintColor {
UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect rect = (CGRect){ CGPointZero, self.size };
CGContextSetBlendMode(context, kCGBlendModeNormal);
[self drawInRect:rect];
CGContextSetBlendMode(context, kCGBlendModeSourceIn);
[tintColor setFill];
CGContextFillRect(context, rect);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
In iOS7, they've introduced tintColor property on UIImageView and renderingMode on UIImage. See my example at https://stackoverflow.com/a/19125120/1570970
With iOS 7.0, you can also just do this to tint a basic UIImageView:
UIImage *iconImage = [[UIImage imageNamed:#"myImageName"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
UIImageView *icon = [[UIImageView alloc] initWithImage:iconImage];
icon.tintColor = [UIColor redColor];
Note that in the accepted answer by fabb, the "surrounding" code for making a UIImage gave me the wrong resolution of images on retina screen. To fix, change:
UIGraphicsBeginImageContext(myIconImage.size);
to:
UIGraphicsBeginImageContextWithOptions(myIconImage.size, NO, 0.0);
The last parameter which is set to 0.0 is scale, and according to Apple documentation:
"If you specify a value of 0.0, the scale factor is set to the scale
factor of the device’s main screen".
Dont have the permission to comment, and editing seems a bit rude, so I mention this in an answer.
Just in case someone encounters this same problem.
UIImageView (or any view for that matter) has a background color which is RGBA. The alpha in the color may do what you need without inventing something new.
Not my work, but i've successfully used this approach:
http://coffeeshopped.com/2010/09/iphone-how-to-dynamically-color-a-uiimage
I wanted to shade my image views in my custom UIButton subclass and the other solutions didn't do what I wanted. I needed to darken "tint" the image color. Here's how to change the brightness using CoreImage.
Make sure you add CoreImage.framework to your project's libraries. (Link Binary with Libraries)
UIImage shade method
- (UIImage *)shadeImage:(UIImage *)image {
CIImage *inputImage = [CIImage imageWithCGImage:image.CGImage];
CIContext *context = [CIContext contextWithOptions:nil];
CIFilter *filter = [CIFilter filterWithName:#"CIColorControls"
keysAndValues:kCIInputImageKey, inputImage,
#"inputBrightness", [NSNumber numberWithFloat:-.5], nil];
CIImage *outputImage = [filter outputImage];
CGImageRef cgImage = [context createCGImage:outputImage fromRect:[outputImage extent]];
UIImage *newImage = [UIImage imageWithCGImage:cgImage scale:image.scale orientation:image.imageOrientation];
CGImageRelease(cgImage);
return newImage;
}
You'll want to store a copy of the context as an ivar, rather than recreate it.
No answers will help me on stack overflow: our designers draw UI elements with various forms, various alpha values (and "alpha-holes"). In most cases, this is 32-Bit PNG file with alpha channel, which comprises black & white pixels (of all possible intensities). After tinting such a picture I had to get this tinted result: white pixels - tinted over more, and dark pixels - less. And all this in view of alpha channel. And i wrote this method for my UIImage category. Maybe it not high efficient, but it work as clock:) Here it is:
- (UIImage *)imageTintedWithColor:(UIColor *)color {
UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
CGContextSetBlendMode(context, kCGBlendModeCopy);
[color setFill];
CGContextFillRect(context, rect);
[self drawInRect:rect blendMode:kCGBlendModeXOR alpha:1.0];
CGContextSetBlendMode(context, kCGBlendModeXOR);
CGContextFillRect(context, rect);
[self drawInRect:rect blendMode:kCGBlendModeMultiply alpha:1.0];
UIImage *coloredImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return coloredImage;
}
First I want to thank fabb for his exceptional solution which has helped me to accomplish my task to tint half transparent Icons. Because I needed a solution for C# (Monotouch) I had to translate his code. Here is what I came up with. Just copy paste this into your code and add your half transparent Image and your done.
So again all credits go to fabb. This is just to kick start C# users :)
//TINT COLOR IMAGE
UIImageView iImage = new UIImageView(new RectangleF(12, 14, 24,24));
iImage.ContentMode = UIViewContentMode.ScaleAspectFit;
iImage.Image = _dataItem.Image[0] as UIImage;
UIGraphics.BeginImageContextWithOptions(iImage.Bounds.Size, false, UIScreen.MainScreen.Scale);
CGContext context = UIGraphics.GetCurrentContext();
context.TranslateCTM(0, iImage.Bounds.Size.Height);
context.ScaleCTM(1.0f, -1.0f);
RectangleF rect = new RectangleF(0,0, iImage.Bounds.Width, iImage.Bounds.Height);
// draw black background to preserve color of transparent pixels
context.SetBlendMode(CGBlendMode.Normal);
UIColor.Black.SetFill();
context.FillRect(rect);
// draw original image
context.SetBlendMode(CGBlendMode.Normal);
context.DrawImage(rect, iImage.Image.CGImage);
// tint image (loosing alpha) - the luminosity of the original image is preserved
context.SetBlendMode(CGBlendMode.Color);
UIColor.Orange.SetFill();
context.FillRect(rect);
// mask by alpha values of original image
context.SetBlendMode(CGBlendMode.DestinationIn);
context.DrawImage(rect, iImage.Image.CGImage);
UIImage coloredImage = UIGraphics.GetImageFromCurrentImageContext();
UIGraphics.EndImageContext();
iImage = new UIImageView(coloredImage);
iImage.Frame = new RectangleF(12, 14, 24,24);
//END TINT COLOR IMAGE
cell.Add(iImage);
i have a view with uiimageview i assign this uiimageview image by camera..now i want to do some drawing onto image....using coregraphics.i want to do something like this... select an area by touching and drawing line when line joins something like circle or any shape..i want to change that particular area in to something else for example change color there.turn that into grayscale.. till now i am able to draw line...here is an image of line drawn over a uiimage view...
but i am unable to figure it out how do i draw at imageview's image..mean how to modify imageview's image???
also i want to restore image when click on clear button or something like undo..does someone knows how to achieve this?
and
how do i create a rectangle when click on crop button move the rectangle any where on the screen...and then push the button to crop the image...and then save cropped image..
These are the steps:
Create a CGBitmapContext matching the image's colorspace and dimensions.
Draw the image into that context.
Draw whatever you want on top of the image.
Create a new image from the context.
Dispose off the context.
Here's a method that takes an image, draws something on top of it and returns a new UIImage with modified contents:
- (UIImage*)modifiedImageWithImage:(UIImage*)uiImage
{
// build context to draw in
CGImageRef image = uiImage.CGImage;
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGContextRef ctx = CGBitmapContextCreate(NULL,
CGImageGetWidth(image), CGImageGetHeight(image),
8, CGImageGetWidth(image) * 4,
colorspace, kCGImageAlphaPremultipliedLast);
CGColorSpaceRelease(colorspace);
// draw original image
CGRect r = CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image));
CGContextSetBlendMode(ctx, kCGBlendModeCopy);
CGContextDrawImage(ctx, r, image);
CGContextSetBlendMode(ctx, kCGBlendModeNormal);
// draw something
CGContextAddEllipseInRect(ctx, CGRectInset(r, 10, 10));
CGContextSetRGBStrokeColor(ctx, 1.0f, 1.0f, 1.0f, 0.5f);
CGContextSetLineWidth(ctx, 16.0f);
CGContextDrawPath(ctx, kCGPathStroke);
CGContextAddEllipseInRect(ctx, CGRectInset(r, 10, 10));
CGContextSetRGBStrokeColor(ctx, 0.7f, 0.0f, 0.0f, 1.0f);
CGContextSetLineWidth(ctx, 4.0f);
CGContextDrawPath(ctx, kCGPathStroke);
// create resulting image
image = CGBitmapContextCreateImage(ctx);
UIImage* newImage = [[[UIImage alloc] initWithCGImage:image] autorelease];
CGImageRelease(image);
CGContextRelease(ctx);
return newImage;
}
To restore to old image, just keep a reference to it.
The cropping thing is not related to the above and you should create a new question for that.
A lot easier solution would be
(UIImage *) modifyImage:(UIImage *)inputImage
{
UIGraphicsBeginImageContext(inputImage.size);
[inputImage drawInRect:CGRectMake(0, 0, inputImage.size.width, inputImage.size.height);
CGContextRef ctx = UIGraphicsGetCurrentContext();
//Drawing code using above context goes here
/*
*
*/
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage;
}
Take a look at Overview of Quartz 2D for information on using Quartz 2D on iPhone.
How can i take an UIImage and give it a black border programmatically?
If i can receive code, it will be great.
tnx
If you only need to display the border you can do that with Core Animation on the UIImageView's layer. If you need to do it on the image itself then you will need to create a new image, draw the old image into the new image and then draw a rect on top of it.
- (UIImage*)imageWithBorderFromImage:(UIImage*)source;
{
CGSize size = [source size];
UIGraphicsBeginImageContext(size);
CGRect rect = CGRectMake(0, 0, size.width, size.height);
[source drawInRect:rect blendMode:kCGBlendModeNormal alpha:1.0];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 1.0, 0.5, 1.0, 1.0);
CGContextStrokeRect(context, rect);
UIImage *testImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return testImg;
}
This will put a pink border on an image and return the new image.
I'd have a look at this:
Can I Edit the Pixels of the UIImage's Property CGImage
As for the black border part, I assume you can figure that one out. Just iterate along each side and change the pixels to (0,0,0,255) for a certain amount.