CODEWITHSUNDEEP
objective-cxcodecocoa-touchuiimage
RaysonK
RaysonK

Reputation: 553

Writing text to a UIImage

I'm trying to write a number inside of an image of a block. I've been looking up how to do this, and I found a couple different ways to do it. Problem is, neither of them work. I've tried this and this, but they both cause an error in the contact log that says invalid context 0x0. Anyone know what can cause that?

EDIT:

I should probably mention where I'm trying to implement this. I have a class called Blok that extends NSObject and holds a UIImage. That UIImage is used in another class's drawRect method, and is also what I want to have text on.

Here's where I initialize the image:

-(id)initWithType:(NSString*)theType andSymbol:(NSString*)theSymbol {

    self = [super init];
    if (self) {

        image = [[UIImage alloc] init];

        type = theType;
        symbol = theSymbol;
    }
    return self;
}

And here is where it gets set later on:

-(void)setImage:(UIImage*)theImage {

    image = theImage;

    image = [self addText:symbol atPoint:CGPointMake(0, 0) withFont:[UIFont fontWithName:@"Helvetica" size:12] ofColor:[UIColor blackColor]];

}

The method call is to the method shown below, given by H2CO3:

- (UIImage *) addText: (NSString *) str atPoint: (CGPoint) point withFont: (UIFont *) font ofColor: (UIColor *) color {

    int w = image.size.width;
    int h = image.size.height;

    // create empty bitmap context
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB ();
    CGContextRef ctx = CGBitmapContextCreate (NULL, w, h, 8, w * 4, colorSpace, kCGImageAlphaPremultipliedFirst);
    CGContextSetInterpolationQuality (ctx, kCGInterpolationHigh);

    // draw the image and the text on the bitmap context
    CGContextDrawImage (ctx, CGRectMake (0, 0, h, w), image.CGImage);
    char *text = (char *)[str cStringUsingEncoding: NSASCIIStringEncoding];
    CGContextSetTextDrawingMode (ctx, kCGTextFill);
    CGFloat *comp = CGColorGetComponents ([color CGColor]);
    CGContextSetRGBFillColor (ctx, comp[0], comp[1], comp[2], comp[3]);
    CGContextSelectFont (ctx, [[font fontName] UTF8String], [font pointSize], kCGEncodingMacRoman);
    CGContextShowTextAtPoint (ctx, point.x, h - point.y, text, strlen (text));

    // get the image as a UIImage and clean up
    CGImageRef imageMasked = CGBitmapContextCreateImage (ctx);
    UIImage *img = [UIImage imageWithCGImage: imageMasked];
    CGContextRelease (ctx);
    CGImageRelease (imageMasked);
    CGColorSpaceRelease (colorSpace);

    return img;

}

I tweaked it a bit to suit the program. Unfortunately, this seems to be causing a bad access error...

Upvotes: 1

Views: 2163

Answers (2)

RaysonK
RaysonK

Reputation: 553

After dealing with this a little longer than I would like, I'm just going to use a UILabel in the drawRect method.

EDIT: Using drawAtPoint in the drawRect method, working just fine now.

Upvotes: 0

user529758
user529758

Reputation:

See how I implemented this here: https://github.com/H2CO3/UIImage-Editor/blob/master/UIImage%2BEditor.m

Especially, take a look at the

- (UIImage *) addText: (NSString *) str atPoint: (CGPoint) point withFont: (UIFont *) font ofColor: (UIColor *) color

method.

Upvotes: 2

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