How to compare UIColors?
https://stackoverflow.com/questions/970475
-
13-09-2019 - |
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I'd like to check the color set for a background on a UIImageView. I've tried:
if(myimage.backgroundColor == [UIColor greenColor]){
...}
else{
...}
but that doesn't work, even when I know the color is green, it always falls into the else part.
Also, is there a way to output the current color in the debug console.
p [myimage backgroundColor]
and
po [myimage backgroundColor]
don't work.
Solution
Have you tried [myColor isEqual:someOtherColor] ?
OTHER TIPS
As zoul pointed out in the comments, isEqual: will return NO when comparing colors that are in different models/spaces (for instance #FFF with [UIColor whiteColor]). I wrote this UIColor extension that converts both colors to the same color space before comparing them:
- (BOOL)isEqualToColor:(UIColor *)otherColor {
CGColorSpaceRef colorSpaceRGB = CGColorSpaceCreateDeviceRGB();
UIColor *(^convertColorToRGBSpace)(UIColor*) = ^(UIColor *color) {
if (CGColorSpaceGetModel(CGColorGetColorSpace(color.CGColor)) == kCGColorSpaceModelMonochrome) {
const CGFloat *oldComponents = CGColorGetComponents(color.CGColor);
CGFloat components[4] = {oldComponents[0], oldComponents[0], oldComponents[0], oldComponents[1]};
CGColorRef colorRef = CGColorCreate( colorSpaceRGB, components );
UIColor *color = [UIColor colorWithCGColor:colorRef];
CGColorRelease(colorRef);
return color;
} else
return color;
};
UIColor *selfColor = convertColorToRGBSpace(self);
otherColor = convertColorToRGBSpace(otherColor);
CGColorSpaceRelease(colorSpaceRGB);
return [selfColor isEqual:otherColor];
}
This might be a bit too late, but CoreGraphics has an easier API to achieve this:
CGColorEqualToColor(myColor.CGColor, [UIColor clearColor].CGColor)
Like the documentation says:
Indicates whether two colors are equal. Two colors are equal if they have equal color spaces and numerically equal color components.
This solves a lot trouble and leaking/custom algorithms.
samvermette's solution translated to swift:
extension UIColor {
func isEqualToColor(otherColor : UIColor) -> Bool {
if self == otherColor {
return true
}
let colorSpaceRGB = CGColorSpaceCreateDeviceRGB()
let convertColorToRGBSpace : ((color : UIColor) -> UIColor?) = { (color) -> UIColor? in
if CGColorSpaceGetModel(CGColorGetColorSpace(color.CGColor)) == CGColorSpaceModel.Monochrome {
let oldComponents = CGColorGetComponents(color.CGColor)
let components : [CGFloat] = [ oldComponents[0], oldComponents[0], oldComponents[0], oldComponents[1] ]
let colorRef = CGColorCreate(colorSpaceRGB, components)
let colorOut = UIColor(CGColor: colorRef!)
return colorOut
}
else {
return color;
}
}
let selfColor = convertColorToRGBSpace(color: self)
let otherColor = convertColorToRGBSpace(color: otherColor)
if let selfColor = selfColor, otherColor = otherColor {
return selfColor.isEqual(otherColor)
}
else {
return false
}
}
}
#import "UIColor-Expanded.h"
//https://github.com/thetaplab/uicolor-utilities
//RGB distance
CGFloat distance = sqrtf(powf((clr0.red - clr1.red), 2) + powf((clr0.green - clr1.green), 2) + powf((clr0.blue - clr1.blue), 2) );
if(distance<=minDistance){
....
}else{
...
}
This UIColor extension works fine provided that the compared colors can be converted into RGB format, which should be most of the cases.
public extension UIColor {
static func == (l: UIColor, r: UIColor) -> Bool {
var l_red = CGFloat(0); var l_green = CGFloat(0); var l_blue = CGFloat(0); var l_alpha = CGFloat(0)
guard l.getRed(&l_red, green: &l_green, blue: &l_blue, alpha: &l_alpha) else { return false }
var r_red = CGFloat(0); var r_green = CGFloat(0); var r_blue = CGFloat(0); var r_alpha = CGFloat(0)
guard r.getRed(&r_red, green: &r_green, blue: &r_blue, alpha: &r_alpha) else { return false }
return l_red == r_red && l_green == r_green && l_blue == r_blue && l_alpha == r_alpha
}
}
At least with this extension:
UIColor.whiteColor == UIColor(hex: "#FFFFFF") // true
UIColor.black == UIColor(red: 0, green: 0, blue: 0, alpha: 1) // true
Both comparisons would return false if compared using the native UColor.isEqual(...)
I wrote this category. If isEqual: does return NO, it will test if further comparison of different components might still match. If possible, different models are still compared.
@implementation UIColor (Matching)
-(BOOL)matchesColor:(UIColor *)color error:(NSError *__autoreleasing *)error
{
UIColor *lhs = self;
UIColor *rhs = color;
if([lhs isEqual:rhs]){ // color model and values are the same
return YES;
}
CGFloat red1, red2, green1, alpha1, green2, blue1, blue2, alpha2;
BOOL lhsSuccess = [lhs getRed:&red1 green:&green1 blue:&blue1 alpha:&alpha1];
BOOL rhsSuccess = [rhs getRed:&red2 green:&green2 blue:&blue2 alpha:&alpha2];
if((!lhsSuccess && rhsSuccess) || (lhsSuccess && !rhsSuccess)){ // one is RGBA, one color not.
CGFloat r,g,b,a;
if(!lhsSuccess){ // lhs color could be a monochrome
const CGFloat *components = CGColorGetComponents(lhs.CGColor);
if([lhs _colorSpaceModel] == kCGColorSpaceModelMonochrome){
r = g = b = components[0];
a = components[1];
return r == red2 && g == green2 && b == blue2 && a == alpha2;
}
} else { // rhs color could be a monochrome
const CGFloat *components = CGColorGetComponents(rhs.CGColor);
if([rhs _colorSpaceModel] == kCGColorSpaceModelMonochrome){
r = g = b = components[0];
a = components[1];
return r == red1 && g == green1 && b == blue1 && a == alpha1;
}
}
NSError *aError = [[NSError alloc] initWithDomain:@"UIColorComparision" code:-11111 userInfo:[self _colorComparisionErrorUserInfo]];
*error = aError;
return NO;
} else if (!lhsSuccess && !rhsSuccess){ // both not RGBA, lets try HSBA
CGFloat hue1,saturation1,brightness1;
CGFloat hue2,saturation2,brightness2;
lhsSuccess = [lhs getHue:&hue1 saturation:&saturation1 brightness:&brightness1 alpha:&alpha1];
rhsSuccess = [lhs getHue:&hue2 saturation:&saturation2 brightness:&brightness2 alpha:&alpha2];
if((!lhsSuccess && rhsSuccess) || (lhsSuccess && !rhsSuccess)){
NSError *aError = [[NSError alloc] initWithDomain:@"UIColorComparision" code:-11111 userInfo:[self _colorComparisionErrorUserInfo]];
*error = aError;
return NO;
} else if(!lhsSuccess && !rhsSuccess){ // both not HSBA, lets try monochrome
CGFloat white1, white2;
lhsSuccess = [lhs getWhite:&white1 alpha:&alpha1];
rhsSuccess = [rhs getWhite:&white2 alpha:&alpha2];
if((!lhsSuccess && rhsSuccess) || (lhsSuccess && !rhsSuccess)){
NSError *aError = [[NSError alloc] initWithDomain:@"UIColorComparision" code:-11111 userInfo:[self _colorComparisionErrorUserInfo]];
*error = aError;
return NO;
} else {
return white1 == white2 && alpha1 == alpha2;
}
} else {
return hue1 == hue2 && saturation1 == saturation2 && brightness1 == brightness2 && alpha1 == alpha2;
}
} else {
return (red1 == red2 && green1 == green2 && blue1 == blue2 && alpha1 == alpha2);
}
}
-(NSDictionary *)_colorComparisionErrorUserInfo{
NSDictionary *userInfo = @{
NSLocalizedDescriptionKey: NSLocalizedString(@"Comparision failed.", nil),
NSLocalizedFailureReasonErrorKey: NSLocalizedString(@"The colors models are incompatible. Or the color is a pattern.", nil),
};
return userInfo;
}
- (CGColorSpaceModel)_colorSpaceModel {
return CGColorSpaceGetModel(CGColorGetColorSpace(self.CGColor));
}
@end
UIColor *green1 = [UIColor greenColor];
UIColor *green2 = [UIColor colorWithRed:0 green:1 blue:0 alpha:1];
UIColor *yellow = [UIColor yellowColor];
UIColor *grey1 = [UIColor colorWithWhite:2.0/3.0 alpha:1];
UIColor *grey2 = [UIColor lightGrayColor];
NSError *error1, *error2, *error3, *error4, *error5;
BOOL match1 = [green1 matchesColor:green2 error:&error1]; // YES
BOOL match2 = [green1 matchesColor:yellow error:&error2]; // NO
BOOL match3 = [green1 matchesColor:grey1 error:&error3]; // NO
BOOL match4 = [grey1 matchesColor:grey2 error:&error4]; // YES
BOOL match5 = [grey1 matchesColor:[UIColor colorWithPatternImage:[UIImage imageNamed:@"bg.png"]]
error:&error5]; // NO, Error
When you're comparing
myimage.backgroundColor == [UIColor greenColor]like this if you havent change the backgroundColor to green before that statement it is not working.
I had same problem in my color game and i solved that by using simple difference equation in RGB colors you can quick take a look that short code sample ColorProcess from here
its like victors answer
GFloat distance = sqrtf(powf((clr0.red - clr1.red), 2) + powf((clr0.green - clr1.green), 2) + powf((clr0.blue - clr1.blue), 2) );
if(distance<=minDistance){
....
}else{
…
}
Instead of that code sample you can use
include "UIColorProcess.h"
..
float distance = [UIColorProcess findDistanceBetweenTwoColor:[UIColor redColor] secondColor:[UIColor blueColor]];
and of course if it returns 0 that means you are comparing too similar color. return range is something like (0.0f - 1.5f)..
Some weird rounding errors can occur. That can be the reason a object set to a color and the color you set it to do not match exactly.
This is how I solved it:
private func compareColors (c1:UIColor, c2:UIColor) -> Bool{
// some kind of weird rounding made the colors unequal so had to compare like this
var red:CGFloat = 0
var green:CGFloat = 0
var blue:CGFloat = 0
var alpha:CGFloat = 0
c1.getRed(&red, green: &green, blue: &blue, alpha: &alpha)
var red2:CGFloat = 0
var green2:CGFloat = 0
var blue2:CGFloat = 0
var alpha2:CGFloat = 0
c2.getRed(&red2, green: &green2, blue: &blue2, alpha: &alpha2)
return (Int(green*255) == Int(green2*255))
}
This code can be improved by not only comparing 1 but comparing all the components. Eg red+green+blue+alpha == red2+green2+blue2+alpha2
I'm using this extension which is working for me in all cases.
/***** UIColor Extension to Compare colors as string *****/
@interface UIColor (compare)
- (BOOL)compareWithColor:(UIColor *)color;
@end
@implementation UIColor(compare)
- (BOOL)compareWithColor:(UIColor *)color {
return ([[[CIColor colorWithCGColor:self.CGColor] stringRepresentation] isEqualToString:[[CIColor colorWithCGColor:color.CGColor] stringRepresentation]]);
}
@end
/**** End ****/
Hope helps some one.
Note: #ffffff does equal [UIColor whiteColor] by this extension
What about:
+(BOOL)color:(UIColor *)color1 matchesColor:(UIColor *)color2
{
CGFloat red1, red2, green1, green2, blue1, blue2, alpha1, alpha2;
[color1 getRed:&red1 green:&green1 blue:&blue1 alpha:&alpha1];
[color2 getRed:&red2 green:&green2 blue:&blue2 alpha:&alpha2];
return (red1 == red2 && green1 == green2 && blue1 == blue2 && alpha1 == alpha2);
}
Here is an extension to switch to the RGC Space Color in Swift:
extension UIColor {
func convertColorToRGBSpaceColor() -> UIColor {
let colorSpaceRGB = CGColorSpaceCreateDeviceRGB()
let oldComponents = CGColorGetComponents(self.CGColor)
let components = [oldComponents[0], oldComponents[0], oldComponents[0], oldComponents[1]]
let colorRef = CGColorCreate(colorSpaceRGB, components)
let convertedColor = UIColor(CGColor: colorRef!)
return convertedColor
}
}
Extension to UIColor, using Swift 2.2 features. Note however that because the R G B A values are compared, and these are CGFloat, rounding errors can make that the colours are non returned as equal if they are not exactly the same (e.g. they have not been originally created using the exact same properties in the init(...)!).
/**
Extracts the RGBA values of the colors and check if the are the same.
*/
public func isEqualToColorRGBA(color : UIColor) -> Bool {
//local type used for holding converted color values
typealias colorType = (red : CGFloat, green : CGFloat, blue : CGFloat, alpha : CGFloat)
var myColor : colorType = (0,0,0,0)
var otherColor : colorType = (0,0,0,0)
//getRed returns true if color could be converted so if one of them failed we assume that colors are not equal
guard getRed(&myColor.red, green: &myColor.green, blue: &myColor.blue, alpha: &myColor.alpha) &&
color.getRed(&otherColor.red, green: &otherColor.green, blue: &otherColor.blue, alpha: &otherColor.alpha)
else {
return false
}
log.debug("\(myColor) = \(otherColor)")
//as of Swift 2.2 (Xcode 7.3.1), tuples up to arity 6 can be compared with == so this works nicely
return myColor == otherColor
}
UIColor extension
- (CGFloat)accuracyCompareWith:(UIColor *)color {
CIColor *c1 = [[CIColor alloc] initWithColor:self];
CIColor *c2 = [[CIColor alloc] initWithColor:color];
BOOL hasAlpha = c1.numberOfComponents == 4 && c2.numberOfComponents == 4;
NSInteger numberOfComponents = hasAlpha ? 4 : 3;
CGFloat colorMax = 1.0;
CGFloat p = colorMax / 100.0;
CGFloat redP = fabs(c1.red / p - c2.red / p);
CGFloat greenP = fabs(c1.green / p - c2.green / p);
CGFloat blueP = fabs(c1.blue / p - c2.blue / p);
CGFloat alphaP = 0;
if (hasAlpha)
alphaP = fabs(c1.alpha / p - c2.alpha / p);
return (redP + greenP + blueP + alphaP) / (CGFloat)numberOfComponents;
}
I have converted raf's answer to Swift 4 (lots of changes in the CGColor API), removed force unwrapping and decreased indentation thanks to generous use of guard:
@extension UIColor {
func isEqualToColor(otherColor: UIColor) -> Bool {
if self == otherColor {
return true
}
let colorSpaceRGB = CGColorSpaceCreateDeviceRGB()
let convertColorToRGBSpace: ((UIColor) -> UIColor?) = { (color) -> UIColor? in
guard color.cgColor.colorSpace?.model == .monochrome else {
return color
}
guard let oldComponents = color.cgColor.components else {
return nil
}
let newComponents = [oldComponents[0], oldComponents[0], oldComponents[0], oldComponents[1]]
guard let colorRef = CGColor(colorSpace: colorSpaceRGB, components: newComponents) else {
return nil
}
return UIColor(cgColor: colorRef)
}
guard let selfColor = convertColorToRGBSpace(self),
let otherColor = convertColorToRGBSpace(otherColor) else {
return false
}
return selfColor.isEqual(otherColor)
}
}
Why not add the extension with equatable protocol? This answer is using the solution of Nicolas Miari. So, if you like this answer, please be welcome to like his answer (second from the top)
The comment of Zoul: Be careful when comparing colors this way, because they have to be in the same color model to be considered equal. For instance, #ffffff does not equal [UIColor whiteColor]
static func == (lhs: UIColor, rhs: UIColor) -> Bool {
let colorSpaceRGB = CGColorSpaceCreateDeviceRGB()
let convertColorToRGBSpace: ((UIColor) -> UIColor?) = { (color) -> UIColor? in
guard color.cgColor.colorSpace?.model == .monochrome else {
return color
}
guard let oldComponents = color.cgColor.components else {
return nil
}
let newComponents = [oldComponents[0], oldComponents[0], oldComponents[0], oldComponents[1]]
guard let colorRef = CGColor(colorSpace: colorSpaceRGB, components: newComponents) else {
return nil
}
return UIColor(cgColor: colorRef)
}
guard let selfColor = convertColorToRGBSpace(lhs),
let otherColor = convertColorToRGBSpace(rhs) else {
return false
}
return selfColor.isEqual(otherColor)
}
While @samvermette's answer is very good, I've found that it can sometimes lead to false negatives when comparing different color types (in my case UIDeviceRGBColor to UICachedDeviceWhiteColor). I fixed it by explicitly creating the color in the `else', too:
- (BOOL)isEqualToColor:(UIColor *)otherColor
{
if (self == otherColor)
return YES;
CGColorSpaceRef colorSpaceRGB = CGColorSpaceCreateDeviceRGB();
UIColor *(^convertColorToRGBSpace)(UIColor*) = ^(UIColor *color)
{
if (CGColorSpaceGetModel(CGColorGetColorSpace(color.CGColor)) == kCGColorSpaceModelMonochrome)
{
const CGFloat *oldComponents = CGColorGetComponents(color.CGColor);
CGFloat components[4] = {oldComponents[0], oldComponents[0], oldComponents[0], oldComponents[1]};
CGColorRef colorRef = CGColorCreate(colorSpaceRGB, components);
UIColor *color = [UIColor colorWithCGColor:colorRef];
CGColorRelease(colorRef);
return color;
}
else
{
const CGFloat *oldComponents = CGColorGetComponents(color.CGColor);
CGFloat components[4] = {oldComponents[0], oldComponents[1], oldComponents[2], oldComponents[3]};
CGColorRef colorRef = CGColorCreate(colorSpaceRGB, components);
UIColor *color = [UIColor colorWithCGColor:colorRef];
CGColorRelease(colorRef);
return color;
}
};
UIColor *selfColor = convertColorToRGBSpace(self);
otherColor = convertColorToRGBSpace(otherColor);
CGColorSpaceRelease(colorSpaceRGB);
return [selfColor isEqual:otherColor];
}
The other solutions didn't work correctly. Here's an approach that works in Swift:
import CoreGraphics
extension UIColor {
/**
Checks for visual equality of two colors regardless of their color space.
- parameter color: The other color for comparison.
- returns: A boolean representing whether the colors are visually the same color.
*/
public func isVisuallyEqualTo(_ color: UIColor) -> Bool {
return rgbaComponents == color.rgbaComponents
}
public var rgbaComponents: [CGFloat] {
var data = [CUnsignedChar](repeating: 0, count: 4)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let context = CGContext(data: &data,
width: 1, height: 1,
bitsPerComponent: 8, bytesPerRow: 4,
space: colorSpace,
bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)
context?.setFillColor(cgColor)
context?.fill(CGRect(x: 0, y: 0, width: 1, height: 1))
return data.map { CGFloat($0) / 255.0 }
}
}
if([myimage.backgroundColor isEqual:[UIColor greenColor]])
