ios: change the colors of a UIImage

Question

I am working on an Iphone application.

I have png pictures that represents symbols. symbols are all black with a transparent background.

Is there a way I can turn the black color into another one? What I'm looking for is something that can help me choose the color I want and when using the symbols (in a UIImage) I can make them appear the color of my choice.

I have searched around and found a framework called OpenCV that can manipulate images but I cant find out how to recolor the picture.

Any help and suggestion is greatly appreciated.

Thank you

Answer 1

The easiest and shortest:

Way to do that in case when you dealing with UIImageView:

Obj-C:

theImageView.image = [theImageView.image imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
[theImageView setTintColor:[UIColor redColor]];

Swift:

let theImageView = UIImageView(image: UIImage(named:"foo")!.imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate))
theImageView.tintColor = UIColor.redColor()

Answer 2

hi you want to change remove/ one specific color means use the below category....

.h file:

#import <UIKit/UIKit.h>

@interface UIImage (Color)

+ (UIImage*)setBackgroundImageByColor:(UIColor *)backgroundColor withFrame:(CGRect )rect;


+ (UIImage*) replaceColor:(UIColor*)color inImage:(UIImage*)image withTolerance:(float)tolerance;

+(UIImage *)changeWhiteColorTransparent: (UIImage *)image;

+(UIImage *)changeColorTo:(NSMutableArray*) array Transparent: (UIImage *)image;

//resizing Stuff...
+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize;

@end

.m file

#import <QuartzCore/QuartzCore.h>
#import "UIImage+Color.h"

@implementation UIImage (Color)




+ (UIImage* )setBackgroundImageByColor:(UIColor *)backgroundColor withFrame:(CGRect )rect{

    // tcv - temporary colored view
    UIView *tcv = [[UIView alloc] initWithFrame:rect];
    [tcv setBackgroundColor:backgroundColor];


    // set up a graphics context of button's size
    CGSize gcSize = tcv.frame.size;
    UIGraphicsBeginImageContext(gcSize);
    // add tcv's layer to context
    [tcv.layer renderInContext:UIGraphicsGetCurrentContext()];
    // create background image now
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
     UIGraphicsEndImageContext();

     return image;
//    [tcv release];

}





+ (UIImage*) replaceColor:(UIColor*)color inImage:(UIImage*)image withTolerance:(float)tolerance {
    CGImageRef imageRef = [image CGImage];

    NSUInteger width = CGImageGetWidth(imageRef);
    NSUInteger height = CGImageGetHeight(imageRef);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    NSUInteger bitmapByteCount = bytesPerRow * height;

    unsigned char *rawData = (unsigned char*) calloc(bitmapByteCount, sizeof(unsigned char));

    CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                                 bitsPerComponent, bytesPerRow, colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);

    CGColorRef cgColor = [color CGColor];
    const CGFloat *components = CGColorGetComponents(cgColor);
    float r = components[0];
    float g = components[1];
    float b = components[2];
    //float a = components[3]; // not needed

    r = r * 255.0;
    g = g * 255.0;
    b = b * 255.0;

    const float redRange[2] = {
        MAX(r - (tolerance / 2.0), 0.0),
        MIN(r + (tolerance / 2.0), 255.0)
    };

    const float greenRange[2] = {
        MAX(g - (tolerance / 2.0), 0.0),
        MIN(g + (tolerance / 2.0), 255.0)
    };

    const float blueRange[2] = {
        MAX(b - (tolerance / 2.0), 0.0),
        MIN(b + (tolerance / 2.0), 255.0)
    };

    int byteIndex = 0;

    while (byteIndex < bitmapByteCount) {
        unsigned char red   = rawData[byteIndex];
        unsigned char green = rawData[byteIndex + 1];
        unsigned char blue  = rawData[byteIndex + 2];

        if (((red >= redRange[0]) && (red <= redRange[1])) &&
            ((green >= greenRange[0]) && (green <= greenRange[1])) &&
            ((blue >= blueRange[0]) && (blue <= blueRange[1]))) {
            // make the pixel transparent
            //
            rawData[byteIndex] = 0;
            rawData[byteIndex + 1] = 0;
            rawData[byteIndex + 2] = 0;
            rawData[byteIndex + 3] = 0;
        }

        byteIndex += 4;
    }

    UIImage *result = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)];

    CGContextRelease(context);
    free(rawData);

    return result;
}

+(UIImage *)changeWhiteColorTransparent: (UIImage *)image
{
    CGImageRef rawImageRef=image.CGImage;

    const float colorMasking[6] = {222, 255, 222, 255, 222, 255};

    UIGraphicsBeginImageContext(image.size);
    CGImageRef maskedImageRef=CGImageCreateWithMaskingColors(rawImageRef, colorMasking);
    {
        //if in iphone
        CGContextTranslateCTM(UIGraphicsGetCurrentContext(), 0.0, image.size.height);
        CGContextScaleCTM(UIGraphicsGetCurrentContext(), 1.0, -1.0); 
    }

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, image.size.width, image.size.height), maskedImageRef);
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    CGImageRelease(maskedImageRef);
    UIGraphicsEndImageContext();    
    return result;
}




+(UIImage *)changeColorTo:(NSMutableArray*) array Transparent: (UIImage *)image
{
    CGImageRef rawImageRef=image.CGImage;

//    const float colorMasking[6] = {222, 255, 222, 255, 222, 255};

     const float colorMasking[6] = {[[array objectAtIndex:0] floatValue], [[array objectAtIndex:1] floatValue], [[array objectAtIndex:2] floatValue], [[array objectAtIndex:3] floatValue], [[array objectAtIndex:4] floatValue], [[array objectAtIndex:5] floatValue]};


    UIGraphicsBeginImageContext(image.size);
    CGImageRef maskedImageRef=CGImageCreateWithMaskingColors(rawImageRef, colorMasking);
    {
        //if in iphone
        CGContextTranslateCTM(UIGraphicsGetCurrentContext(), 0.0, image.size.height);
        CGContextScaleCTM(UIGraphicsGetCurrentContext(), 1.0, -1.0); 
    }

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, image.size.width, image.size.height), maskedImageRef);
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    CGImageRelease(maskedImageRef);
    UIGraphicsEndImageContext();    
    return result;
}

+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
    //UIGraphicsBeginImageContext(newSize);
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newImage;
}



@end

i changed the removed white color to transparent by this code....

the call will be...

 self.rawImage.image=[UIImage changeWhiteColorTransparent:originalStateImage];

i hope this idea will help you....

Answer 3

hi use this category file to change the image entire color....

.h file:

#import <UIKit/UIKit.h>

@interface UIImage (AddtionalFunctionalities)

//TintColor...
- (UIImage *)imageWithTint:(UIColor *)tintColor;
//scale and resize...
-(UIImage*)scaleToSize:(CGSize)size;

@end

.m file:

#import "UIImage+AddtionalFunctionalities.h"

@implementation UIImage (AddtionalFunctionalities)


- (UIImage *)imageWithTint:(UIColor *)tintColor 
{
    // Begin drawing
    CGRect aRect = CGRectMake(0.f, 0.f, self.size.width, self.size.height);
    CGImageRef alphaMask;

    //
    // Compute mask flipping image
    //
    {
        UIGraphicsBeginImageContext(aRect.size);        
        CGContextRef c = UIGraphicsGetCurrentContext(); 

        // draw image
        CGContextTranslateCTM(c, 0, aRect.size.height);
        CGContextScaleCTM(c, 1.0, -1.0);
        [self drawInRect: aRect];

        alphaMask = CGBitmapContextCreateImage(c);

        UIGraphicsEndImageContext();
    }

    //
    UIGraphicsBeginImageContext(aRect.size);

    // Get the graphic context
    CGContextRef c = UIGraphicsGetCurrentContext(); 

    // Draw the image
    [self drawInRect:aRect];

    // Mask
    CGContextClipToMask(c, aRect, alphaMask);

    // Set the fill color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextSetFillColorSpace(c, colorSpace);

    // Set the fill color
    CGContextSetFillColorWithColor(c, tintColor.CGColor);

    UIRectFillUsingBlendMode(aRect, kCGBlendModeNormal);

    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();    

    // Release memory
    CGColorSpaceRelease(colorSpace);
    CGImageRelease(alphaMask);

    return img;
}


-(UIImage*)scaleToSize:(CGSize)size
{
    // Create a bitmap graphics context
    // This will also set it as the current context
    UIGraphicsBeginImageContext(size);

    // Draw the scaled image in the current context
    [self drawInRect:CGRectMake(0, 0, size.width, size.height)];

    // Create a new image from current context
    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();

    // Pop the current context from the stack
    UIGraphicsEndImageContext();

    // Return our new scaled image
    return scaledImage;
}

@end

the method call will be :

 self.outputImage.image=[sourceImage imageWithTint:[UIColor redColor]];

if u want to use the image means use this:

self.outputImage.image=[sourceImage imageWithTint:[UIColor colorWithPatternImage:[UIImage imageNamed: @"red.jpg"]]];

i hope this will help you...

Answer 4

Set the Image rendering mode then for color purpose use tintcolor property.

yourImageView.image = [image imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
[yourImageView setTintColor:[UIColor redColor]];

Answer 5

For iOS 13.0

Obj-C:

self.yourImageView.image = [self.yourImageView.image imageWithTintColor:[UIColor.redColor]];

Swift:

yourImageView.image = yourImageView.image.withTintColor(UIColor.red);

If the image comes from the Asset Catalog, you can change the rendering in the Attribute Inspector

Answer 6

You can create UIView which store UIImageView and change UIview background Color.

UIView *viewForImage = ....;
UIImageView *imageView = .....;
...

[viewForImage addSubview: imageView];
[self.view addSubview:viewForImage];
...

and then use for example

[viewForImage setBackgroundColor: [UIColor redColor]];

Answer 7

For playing with images using objective-c, mainly you have to use Quartz 2D/CoreGraphics framework. I suppose it will be the easiest way for you to accomplish your task.

The link to Quartz 2D guideline is here , the guideline is pretty comprehensive. Just have a look somewhere in filling the bitmap with color.

Also I've some records about the heavy image processing in my blog, you can have a look, it might be helpfull. http://levonp.blogspot.de/2012/05/quartz-getting-diff-images-of-two.html

Of course you can do it also using more advanced stuffs like OpenGL, OpenCV, etc.

Answer 8

A very simple solution to change the color of the image. Idea: extensions for UIImage and UIImageView.

Swift 3, Xcode 8.1. https://stackoverflow.com/a/40884483/4488252

Code sample from my answer (link above):

// use extension UIImage
newImageView = createNewImageView(x: 100)
newImageView.image =  UIImage(named: "Apple")?.imageWithColor(newColor: UIColor.blue)

// use extension UIImageView
newImageView = createNewImageView(x: 160)
newImageView.image =  UIImage(named: "Apple")
newImageView.imageColor = UIColor.green