I was wondering if anyone knows how to take an Image using CoreGraphics and add a gloss effect like you see on iOS. Specifically I want to take an image that gets downloaded from the web and style it like this. I've searched high and low and all I found was examples of how to do it in PhotoShop and not in code. Any code snippets or pointers to resources that can help I would appreciate.
I figured it out on my own after wasting a few hours trying to figure this out... Here's my code:
static void addRoundedRectToPath(CGContextRef context, CGRect rect, float ovalWidth, float ovalHeight) {
float fw, fh;
if (ovalWidth == 0 || ovalHeight == 0) {
CGContextAddRect(context, rect);
return;
}
CGContextSaveGState(context);
CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGContextScaleCTM (context, ovalWidth, ovalHeight);
fw = CGRectGetWidth (rect) / ovalWidth;
fh = CGRectGetHeight (rect) / ovalHeight;
CGContextMoveToPoint(context, fw, fh/2);
CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 1);
CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 1);
CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 1);
CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 1);
CGContextClosePath(context);
CGContextRestoreGState(context);
}
static void addGlossPath(CGContextRef context, CGRect rect) {
CGFloat quarterHeight = CGRectGetMidY(rect) / 2;
CGContextSaveGState(context);
CGContextBeginPath(context);
CGContextMoveToPoint(context, -20, 0);
CGContextAddLineToPoint(context, -20, quarterHeight);
CGContextAddQuadCurveToPoint(context, CGRectGetMidX(rect), quarterHeight * 3, CGRectGetMaxX(rect) + 20, quarterHeight);
CGContextAddLineToPoint(context, CGRectGetMaxX(rect) + 20, 0);
CGContextClosePath(context);
CGContextRestoreGState(context);
}
UIImage *applyIconHighlightToImage(UIImage *icon) {
UIImage *newImage;
CGContextRef context;
CGGradientRef glossGradient;
CGColorSpaceRef rgbColorspace;
CGRect currentBounds = CGRectMake(0, 0, icon.size.width, icon.size.height);
CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMidY(currentBounds));
CGFloat locations[2] = {0.0, 1.0};
CGFloat components[8] = {1.0, 1.0, 1.0, 0.75, 1.0, 1.0, 1.0, 0.2};
UIGraphicsBeginImageContext(icon.size);
context = UIGraphicsGetCurrentContext();
UIGraphicsPushContext(context);
addRoundedRectToPath(context, currentBounds, 10, 10);
CGContextClosePath(context);
CGContextClip(context);
[icon drawInRect:currentBounds];
addGlossPath(context, currentBounds);
CGContextClip(context);
rgbColorspace = CGColorSpaceCreateDeviceRGB();
glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, 2);
CGContextDrawLinearGradient(context, glossGradient, topCenter, midCenter, 0);
UIGraphicsPopContext();
newImage = UIGraphicsGetImageFromCurrentImageContext();
CGGradientRelease(glossGradient);
CGColorSpaceRelease(rgbColorspace);
UIGraphicsEndImageContext();
return newImage;
}
Edit:
Wanted to make sure I gave credit where credit is due. Thanks to Brad Larson for the code on adding a glossy gradient.
I provide code to draw a glossy gradient using Core Graphics in my answer here.
If all that you wish to do is overlay a gloss effect on your image, it may be more performant to generate this using a CAGradientLayer, as decribed by Mirko in his answer there.
Related
I'm trying to add a text to an UIImage and I'm getting a pixelated drawing.
I have tried some other answers with no success:
Drawing on the retina display using CoreGraphics - Image pixelated
Retina display core graphics font quality
Drawing with Core Graphics looks chunky on Retina display
My code:
-(UIImage *)addText:(UIImage *)imgV text:(NSString *)text1
{
int w = self.frame.size.width * 2;
int h = self.frame.size.height * 2;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate
(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
CGContextDrawImage(context, CGRectMake(0, 0, w, h), imgV.CGImage);
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1);
char* text = (char *)[text1 cStringUsingEncoding:NSASCIIStringEncoding];
CGContextSelectFont(context, "Arial", 24, kCGEncodingMacRoman);
// Adjust text;
CGContextSetTextDrawingMode(context, kCGTextInvisible);
CGContextShowTextAtPoint(context, 0, 0, text, strlen(text));
CGPoint pt = CGContextGetTextPosition(context);
float posx = (w/2 - pt.x)/2.0;
float posy = 54.0;
CGContextSetTextDrawingMode(context, kCGTextFill);
CGContextSetRGBFillColor(context, 255, 255, 255, 1.0);
CGContextShowTextAtPoint(context, posx, posy, text, strlen(text));
CGImageRef imageMasked = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return [UIImage imageWithCGImage:imageMasked];
}
Like Peter said, use UIGraphicsBeginImageContextWithOptions. You might want to pass image.scale to the scale attribute (where image.scale is the scale of one of the images you're drawing), or simply use [UIScreen mainScreen].scale.
This code can be made simpler overall. Try something like:
// Create the image context
UIGraphicsBeginImageContextWithOptions(_baseImage.size, NO, _baseImage.scale);
// Draw the image
CGRect rect = CGRectMake(0, 0, _baseImage.size.width, _baseImage.size.height);
[_baseImage drawInRect:rect];
// Get a vertically centered rect for the text drawing
rect.origin.y = (rect.size.height - FONT_SIZE) / 2 - 2;
rect = CGRectIntegral(rect);
rect.size.height = FONT_SIZE;
// Draw the text
UIFont *font = [UIFont boldSystemFontOfSize:FONT_SIZE];
[[UIColor whiteColor] set];
[text drawInRect:rect withFont:font lineBreakMode:NSLineBreakByClipping alignment:NSTextAlignmentCenter];
// Get and return the new image
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
Where text is an NSString object.
I was facing the exact same problem and posted a question last night to which no-one replied. I have combined fnf's suggested changes with Clif Viegas's answer in the following question:
CGContextDrawImage draws image upside down when passed UIImage.CGImage
to come up with the solution. My addText method is slightly different from yours:
+(UIImage *)addTextToImage:(UIImage *)img text:(NSString *)text1{
int w = img.size.width;
int h = img.size.height;
CGSize size = CGSizeMake(w, h);
if (UIGraphicsBeginImageContextWithOptions != NULL) {
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
} else {
UIGraphicsBeginImageContext(size);
}
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0,h);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1);
char* text = (char *)[text1 cStringUsingEncoding:NSASCIIStringEncoding];// \"05/05/09\";
CGContextSelectFont(context, "Times New Roman", 14, kCGEncodingMacRoman);
CGContextSetTextDrawingMode(context, kCGTextFill);
CGContextSetRGBFillColor(context, 0, 0, 0, 1);
//rotate text
CGContextSetTextMatrix(context, CGAffineTransformMakeRotation( -M_PI/8 ));
CGContextShowTextAtPoint(context, 70, 88, text, strlen(text));
CGColorSpaceRelease(colorSpace);
UIGraphicsEndImageContext();
return newImg;
}
In summary, what I have done is add
if (UIGraphicsBeginImageContextWithOptions != NULL) {
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
} else {
UIGraphicsBeginImageContext(size);
}
Remove
// CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
and put
CGContextRef context = UIGraphicsGetCurrentContext();
instead. But this causes the image to be upside down. Hence I put
CGContextTranslateCTM(context, 0,h);
CGContextScaleCTM(context, 1.0, -1.0);
just before
CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
This way you can use CG functions instead of using drawInRect etc.
Don't forget
UIGraphicsEndImageContext
at the end. Hope this helps.
I have used this solution to apply corner radius to UIImage in Quartz. It works fine like I predicted.
However the corners area outside of the image are not transparent but somewhat colored in white:
The image above shows top left corner of processed image that is opaque and not transparent.
I want cropped-out edges to be totally transparent. How can I achieve this?
EDIT: If I want to do this with UIImageView I would already done this. So please keep in mind that I want to do this with Quartz on UIImage object not UIImageView.
SOLUTION: The problem is actually not in the drawing code but rather in writing that image to the file system. I've saved image as JPEG an not as PNG. That's why corners were not transparent cos JPEG does not have alpha filter.
I usually use a custom category implemented on UIImage to crop the images with round corners. This was taken from this answer.
void addRoundedRectToPath(CGContextRef context, CGRect rect, float ovalWidth, float ovalHeight, BOOL top, BOOL bottom)
{
float fw, fh;
if (ovalWidth == 0 || ovalHeight == 0) {
CGContextAddRect(context, rect);
return;
}
CGContextSaveGState(context);
CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGContextScaleCTM (context, ovalWidth, ovalHeight);
fw = CGRectGetWidth (rect) / ovalWidth;
fh = CGRectGetHeight (rect) / ovalHeight;
CGContextMoveToPoint(context, fw, fh/2);
CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 0);
NSLog(#"bottom? %d", bottom);
if (top) {
CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 3);
} else {
CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 0);
}
if (bottom) {
CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 3);
} else {
CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 0);
}
CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 0);
CGContextClosePath(context);
CGContextRestoreGState(context);
}
- (UIImage *)roundCornersOfImage:(UIImage *)source roundTop:(BOOL)top roundBottom:(BOOL)bottom {
int w = source.size.width;
int h = source.size.height;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
CGContextBeginPath(context);
CGRect rect = CGRectMake(0, 0, w, h);
addRoundedRectToPath(context, rect, 4, 4, top, bottom);
CGContextClosePath(context);
CGContextClip(context);
CGContextDrawImage(context, CGRectMake(0, 0, w, h), source.CGImage);
CGImageRef imageMasked = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return [UIImage imageWithCGImage:imageMasked];
}
add these bellow lines in your drawRect method ..
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, rect);
///your another code here
}
after create Context it required to clear another context from that Rect... so after that line add this line CGContextClearRect(context, rect);.
For transparent use this:
const float colorMasking[6] = {1.0, 1.0, 0.0, 0.0, 1.0, 1.0};
yourImage = [UIImage imageWithCGImage: CGImageCreateWithMaskingColors(yourImage.CGImage, colorMasking)];
EDIT : Add this both line in method of UIImage category
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, rect);
The problem is actually not in the drawing code but rather in writing that image to the file system. I've saved image as JPEG an not as PNG. That's why corners were not transparent cos JPEG does not have alpha filter.
Just replaced this line of code:
[UIImageJPEGRepresentation(image, 0.75) writeToFile:path atomically:YES];
... with this one:
[UIImagePNGRepresentation(image) writeToFile:path atomically:YES];
Try this code
Image.layer.cornerRadius = 10.0;
Image.layer.borderColor = [UIColor blackColor].CGColor;
Image.layer.borderWidth = 0.5;
Image.clipsToBounds = YES;
Image.backgroundColor = [UIColor clearColor];
Hope it helps you
EDIT :-
I think you just need to add this :-
Image.clipsToBounds = YES;
I want to draw a gradient inside a polygon using core graphics. I am able to draw a hexagon using the code below but i don't know how to fill this hexagon with a gradient color. Any help will be really appreciated.
- (void)drawRect:(CGRect)rect
{
// Drawing code.
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1.0);
CGContextSetLineWidth(context, 2.0);
CGPoint center;
center = CGPointMake(210.0, 90.0);
CGContextMoveToPoint(context, center.x, center.y + 60.0);
for(int i = 1; i < 6; ++i)
{
CGFloat x = 60.0 * sinf(i * 2.0 * M_PI / 6.0);
CGFloat y = 60.0 * cosf(i * 2.0 * M_PI / 6.0);
CGContextAddLineToPoint(context, center.x + x, center.y + y);
}
CGContextClosePath(context);
CGContextDrawPath(context, kCGPathFillStroke);
}
Use following code for Gradient fill
CGContextRef context = UIGraphicsGetCurrentContext();
CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();
CGFloat colors[] =
{
0.62890625, 0.859375, 10.9921875, 1.00,
0.65625, 0.8046875, 0.9453125, 1.00,
};
CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, sizeof(colors)/(sizeof(colors[0])*4));
CGColorSpaceRelease(rgb);
// now we can actually create the shape and fill it
CGPoint start, end;
CGContextSetRGBFillColor(context, 0, 0, 0.6, 0.1);
CGContextFillEllipseInRect(context, CGRectMake(0.0, 0.0, 100.0, 100.0));
CGContextStrokeEllipseInRect(context, CGRectMake(0.0, 0.0, 100.0, 100.0));
// Gradient
CGRect myrect = CGRectMake(0.0, 0.0, rect.size.width, rect.size.height);
CGContextSaveGState(context);
CGContextClipToRect(context, myrect);
start = CGPointMake(myrect.origin.x, myrect.origin.y + myrect.size.height * 0.25);
end = CGPointMake(myrect.origin.x, myrect.origin.y + myrect.size.height * 1.0);
CGContextDrawLinearGradient(context, gradient, start, end, kCGGradientDrawsBeforeStartLocation);
CGContextRestoreGState(context);
I want to draw a curved line with arrow between two points using the Quartz Core framework in an iPhone Application. How to do that or any what classes are available to do that ?
You can change the co-ordinates as you want
- (void)drawRect:(CGRect)rect {
//DRAW CURVE
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 2.0);
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGContextMoveToPoint(context, 100, 100);
CGContextAddArcToPoint(context, 100,200, 300,200, 100);
CGContextStrokePath(context);
//DRAW LINE
CGContextSetLineWidth(context, 2.0);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGFloat components[] = {0.0, 0.0, 1.0, 1.0};
CGColorRef color = CGColorCreate(colorspace, components);
CGContextSetStrokeColorWithColor(context, color);
CGContextMoveToPoint(context, 0, 0);
CGContextAddLineToPoint(context, 300, 400);
CGContextStrokePath(context);
CGColorSpaceRelease(colorspace);
CGColorRelease(color);
}
I have not really done much programming with Core Graphics. And I tend to stick with QuartzCore now that it does a lot of what I need through the layer property :)
However, I have a UIView, which is currently gradient. I'd like to add rounded corners to this UIView and the layer property does not do this when I draw the gradient:
- (void)drawRect:(CGRect)rect {
CGContextRef currentContext = UIGraphicsGetCurrentContext();
CGGradientRef glossGradient;
CGColorSpaceRef rgbColorspace;
size_t num_locations = 2;
CGFloat locations[2] = { 0.0, 1.0 };
CGFloat components[8] = { 1.0, 1.0, 1.0, 0.95, // Start color
1.0, 1.0, 1.0, 0.60 }; // End color
rgbColorspace = CGColorSpaceCreateDeviceRGB();
glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);
CGRect currentBounds = self.bounds;
CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMaxY(currentBounds));
CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);
CGGradientRelease(glossGradient);
CGColorSpaceRelease(rgbColorspace);
}
I am not really sure where I should be rounding in the drawRect method. Thanks.
Have you checked previous question postings? I read one a while back about masking UIViews. I think the same applies pretty much on all objects which use drawRect
How to mask a square image into an image with round corners in the iPhone SDK?
Here's what I did, and it works fine as far as I can tell.
First, I borrowed Mr NilObject's code snippet from the above mentioned post.
I modified it to fit in an object (as he wrote it as a C function instead of a method)
I subclass UIView to create my own custom view. I overload initWithRect: to make my background transparent.
So basically:
set transparent background (in init), or clipping will be uggly
in drawRect, first clip, then draw inside the clipped area
The following is a working example:
//
// TeleView.m
//
#import "TeleView.h"
#implementation TeleView
/**** in init methods, set background to transparent,
otherwise, clipping shows a black background ****/
- (id) initWithFrame:(CGRect)frame {
if((self = [super initWithFrame:frame])) {
[self setBackgroundColor:[UIColor colorWithWhite:0.0f alpha:0.0f]];
}
return self;
}
- (void) clipCornersToOvalWidth:(float)ovalWidth height:(float)ovalHeight
{
float fw, fh;
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect rect = CGRectMake(0.0f, 0.0f, self.frame.size.width, self.frame.size.height);
if (ovalWidth == 0 || ovalHeight == 0) {
CGContextAddRect(context, rect);
return;
}
CGContextSaveGState(context);
CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGContextScaleCTM (context, ovalWidth, ovalHeight);
fw = CGRectGetWidth (rect) / ovalWidth;
fh = CGRectGetHeight (rect) / ovalHeight;
CGContextMoveToPoint(context, fw, fh/2);
CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 1);
CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 1);
CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 1);
CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 1);
CGContextClosePath(context);
CGContextRestoreGState(context);
}
-(void)drawRect:(CGRect)rect {
CGContextRef currentContext = UIGraphicsGetCurrentContext();
/**** here is what I modified. ****/
[self clipCornersToOvalWidth:20.0f height:20.0f];
CGContextClip(currentContext);
/**** below this is your own code ****/
CGGradientRef glossGradient;
CGColorSpaceRef rgbColorspace;
size_t num_locations = 2;
CGFloat locations[2] = { 0.0, 1.0 };
CGFloat components[8] = { 1.0, 0.0, 0.0, 0.60, // Start color
0.0, 1.0, 0.0, 0.40 }; // End color
rgbColorspace = CGColorSpaceCreateDeviceRGB();
glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);
CGRect currentBounds = self.bounds;
CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMaxY(currentBounds));
CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);
CGGradientRelease(glossGradient);
CGColorSpaceRelease(rgbColorspace);
}
#end
NSArray *colors = [NSArray arrayWithObjects:fromColor.CGColor,toColor.CGColor, nil];
NSNumber *stopOne = [NSNumber numberWithFloat:0.0];
NSNumber *stopTwo = [NSNumber numberWithFloat:1.0];
NSArray *locations = [NSArray arrayWithObjects:stopOne, stopTwo, nil];
CAGradientLayer *headerLayer = [CAGradientLayer layer];
headerLayer.colors = colors;
headerLayer.locations = locations;
headerLayer.borderColor = borderColor.CGColor; // border line color**strong text**
headerLayer.borderWidth = width;// For Thickness of border line
headerLayer.cornerRadius = radius;//For Rounded Corner if You want to make rounded Corner
headerLayer.frame = frame;
[view.layer insertSublayer:headerLayer atIndex:0];
Also make sure to import "QuartzCore" framework