I am drawing a pie chart, each slice has a different color. I need to give the slices a textured look, not just the plain color. Any ideas how to do this? I don't want to use a image to use as a texture for all the possible colors. So I need to generate a texture or something like that. Any ideas. Thank You!
ps: this is an iphone project. (I can't use Core Image)
Use colorWithPatternImage with UIColor.
Edit: Sorry should have read the question properly.
You will need to use a UIGraphicsContext to create an image you can use in colorWithPatternImage. I would suggest using a grayscale image that you can load in, tint with a similar method to this, then use as a pattern in UIColor.
So you would have a method along the lines of this:
- (UIColor *)texturedPatternWithTint:(UIColor *)tint {
UIImage *texture = [UIImage imageNamed:#"texture.png"];
CGRect wholeImage = CGRectMake(0, 0, texture.size.width, texture.size.height);
UIGraphicsBeginImageContextWithOptions(texture.size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, wholeImage, texture.CGImage);
CGContextSetBlendMode(context, kCGBlendModeMultiply);
CGContextSetFillColor(context, CGColorGetComponents(tint.CGColor));
CGContextFillRect(context, self.bounds);
UIImage *tintedTexture = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return [UIColor colorWithPatternImage:tintedTexture];
}
(not tested)
Related
I have an UIImage with some text and would like to apply pattern UIImage as masking. Is this possible ?
I understand that with UILabel we can get this kind of gradient using CAGradientLayer. But can this be done if the source is an UIImage ?
The image may have some symbols/pictures etc other than regular characters and hence UIImage. Also i could reuse the image by applying different masking pattern depending on the context.
is this possible ?
Appreciate your help.
EDIT: Thanks for all your answers.
I understand applying the gradient to a text label or creating an image that has text.
But my goal is to get this.--> Click here
i.e. i have a png with some drawing like a flower with transparent background. I want to apply the gradient to the object inside that picture at runtime with a gradient.png as shown in the picture above. Is that possible with masking ?
Thanks
Looks like you should be able to use CGImageMaskCreate:
- (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage {
CGImageRef maskRef = maskImage.CGImage;
CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
CGImageGetHeight(maskRef),
CGImageGetBitsPerComponent(maskRef),
CGImageGetBitsPerPixel(maskRef),
CGImageGetBytesPerRow(maskRef),
CGImageGetDataProvider(maskRef), NULL, false);
CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);
return [UIImage imageWithCGImage:masked];
}
For a longer discussion check out the comment thread here:
http://iosdevelopertips.com/cocoa/how-to-mask-an-image.html
Yes, it is :)
textField.textColor = [UIColor colorWithPatternImage: [UIImage imageNamed:#"rainbowGradient.png"]];
If you want heavy control, Jason Whyne's idea might work. But I like this one, because it's about 8 lines shorter.
Here's just another way to draw an image of text masking something. It's based on kCGBlendModeSourceIn blending mode: you draw text on a clear background and then draw the fill all over the place.
NSString *theString = ...;
UIFont *theFont = ...;
CGSize stringSize = [theString sizeWithFont:theFont];
// The background must be clear (fully transparent), hence NO as the 2nd argument
UIGraphicsBeginImageContextWithOptions(stringSize, NO, 0);
[theString drawAtPoint:CGPointZero withFont:theFont];
// This effectively colorizes the image. Use a pattern color...
[patternColor set];
UIRectFillUsingBlendMode(CGRectMake(0, 0, stringSize.width, stringSize.height), kCGBlendModeSourceIn);
// ... or an image:
[patternImage drawInRect:CGRectMake(0, 0, stringSize.width, stringSize.height) blendMode:kCGBlendModeSourceIn alpha:1.0f];
UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
sample using mask is fine and works well, but You are leaking.
CGImageMaskCreate and CGImageCreateWithMask do allocate (following "create" -> retain rule)
so You should release mask & image after using:
CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);
UIImage * result = [UIImage imageWithCGImage:masked];
CGImageRelease(mask);
CGImageRelease(masked);
return result;
As per ADC docs:
...
Return Value
A Quartz bitmap image mask. You are responsible for releasing this object by calling CGImageRelease.
I have a sequence of bits for a monochrome image (0 => black, 1 => white). I want to take this data and draw an image on the iPhone in color. If a pixel value == 0, then paint it color1, else color2.
I have gotten absolutely nowhere. Originally, I thought I could use glBitmap, but it is not supported on the iPhone.
Does anyone have an idea of how to do this?
Thanks in advance.
I highly doubt that this is "the" way of doing it, or even a good way of doing it, but since there are no other responses, here is a possible way:
UIGraphicsBeginImageContext(CGSizeMake(width,height));
CGContextRef context = UIGraphicsGetCurrentContext();
UIGraphicsPushContext(context);
for(int y=0;y<height,y++){
for(int x=0;x<width;x++){
int val=map[x+y*width];
if(val==0){
CGContextSetRGBFillColor(context, 0.0,0.0,0.0,1.0);
}else{
CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
}
CGContextFillRect(context,CGRectMake(x,y,1,1));
}
}
UIGraphicsPopContext();
UIImage* image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
Also note, that I have not actually tested this on the iPhone, only on the iPad.
So I have a spritesheet in png format, and have already worked out the coordinates for what I want to display. I'm trying to create a method that will return a UIImage when passed the location information on the spritesheet. I'm just not sure how to use the CGContext stuff along with the the coordinates to return an UIImage.
I was looking to CGContextClipToRect because I think that is the way to do it, but I just can't seem to get it to work.
Something like this
CGSize size = CGSizeMake(xSize, ySize);
UIGraphicsBeginImageContext(size);
//CGContextClipToRect(spriteSheet.size, imageRect);
[spriteSheet drawAtPoint:CGPointMake(xPos, yPos)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
returns only what is in the size Context. I need to be able to "move" this size window around the spritesheet if that makes sense.
Any help would be appreciated.
Thanks,
Mike
I think the call you want to use is CGImageCreateWithImageInRect
newImage = [UIImage imageWithCGImage:CGImageCreateWithImageInRect( [spriteSheet CGImage] , imageRect )];
you need to think of your co-ordinates backwards. The CGSize is fixed. Translate your xPos,yPos so that your sprite appears under the window.
I have a small image from a database and the image's average color need to be altered slightly.
It's a CGImageRef and I thought of creating a CGContext, drawing the image to this context, then subsequently changing the bitmap data somehow and finally rendering it.
But how can I alter the color information?
Thanks for your help!
Check out this Apple Q&A on pixel data manipulation for details on how you might go about that.
Draw a color onto the object like this:
// first draw image
[self.image drawInRect:rect];
// prepare the context to draw into
CGContextRef context = UIGraphicsGetCurrentContext();
// set the blend mode and draw rectangle on top of image
CGContextSetBlendMode(context, kCGBlendModeColor);
CGContextClipToMask(context, self.bounds, image.CGImage); // this restricts drawing to within alpha channel
CGContextSetRGBFillColor(context, 0.75, 0.0, 0.0, 1.0); // this is your color, a light reddish tint
CGContextFillRect(context, rect);
I put this into the drawRect: method of a custom UIView. That UIView has an ivar, UIImage *image that holds the image you want to tint or color.
I've got a UIImageView (full frame and rectangular) that i'm rotating with a CGAffineTransform. The UIImage of the UIImageView fills the entire frame. When the image is rotated and drawn the edges appear noticeably jagged. Is there anything I can do to make it look better? It's clearly not being anti-aliased with the background.
The edges of CoreAnimation layers aren't antialiased by default on iOS. However, there is a key that you can set in Info.plist that enables antialiasing of the edges: UIViewEdgeAntialiasing.
https://developer.apple.com/library/content/documentation/General/Reference/InfoPlistKeyReference/Articles/iPhoneOSKeys.html
If you don't want the performance overhead of enabling this option, a work-around is to add a 1px transparent border around the edge of the image. This means that the 'edges' of the image are no longer on the edge, so don't need special treatment!
New API – iOS 6/7
Also works for iOS 6, as noted by #Chris, but wasn't made public until iOS 7.
Since iOS 7, CALayer has a new property allowsEdgeAntialiasing which does exactly what you want in this case, without incurring the overhead of enabling it for all views in your application! This is a property of CALayer, so to enable this for a UIView you use myView.layer.allowsEdgeAntialiasing = YES.
just add 1px transparent border to your image
CGRect imageRect = CGRectMake(0, 0, image.size.width, image.size.height);
UIGraphicsBeginImageContextWithOptions(imageRect.size, NO, 0.0);
[image drawInRect:CGRectMake(1,1,image.size.width-2,image.size.height-2)];
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
Remember to set the appropriate anti-alias options:
CGContextSetAllowsAntialiasing(theContext, true);
CGContextSetShouldAntialias(theContext, true);
just add "Renders with edge antialiasing" with YES in plist and it will work.
I would totally recommend the following library.
http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/
It contains lots of useful extensions to UIImage that solve this problem and also include code for generating thumbnails etc.
Enjoy!
The best way I've found to have smooth edges and a sharp image is to do this:
CGRect imageRect = CGRectMake(0, 0, self.photo.image.size.width, self.photo.image.size.height);
UIGraphicsBeginImageContextWithOptions(imageRect.size, NO, 0.0);
[self.photo.image drawInRect:CGRectMake(1, 1, self.photo.image.size.width - 2, self.photo.image.size.height - 2)];
self.photo.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
Adding the Info.plist key like some people describe has a big hit on performance and if you use that then you're basically applying it to everything instead of just the one place you need it.
Also, don't just use UIGraphicsBeginImageContext(imageRect.size); otherwise the layer will be blurry. You have to use UIGraphicsBeginImageContextWithOptions like I've shown.
I found this solution from here, and it's perfect:
+ (UIImage *)renderImageFromView:(UIView *)view withRect:(CGRect)frame transparentInsets:(UIEdgeInsets)insets {
CGSize imageSizeWithBorder = CGSizeMake(frame.size.width + insets.left + insets.right, frame.size.height + insets.top + insets.bottom);
// Create a new context of the desired size to render the image
UIGraphicsBeginImageContextWithOptions(imageSizeWithBorder, NO, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
// Clip the context to the portion of the view we will draw
CGContextClipToRect(context, (CGRect){{insets.left, insets.top}, frame.size});
// Translate it, to the desired position
CGContextTranslateCTM(context, -frame.origin.x + insets.left, -frame.origin.y + insets.top);
// Render the view as image
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
// Fetch the image
UIImage *renderedImage = UIGraphicsGetImageFromCurrentImageContext();
// Cleanup
UIGraphicsEndImageContext();
return renderedImage;
}
usage:
UIImage *image = [UIImage renderImageFromView:view withRect:view.bounds transparentInsets:UIEdgeInsetsZero];