How to write a text on image iOS? - ios

Question

In my app I'm trying to add a text on an image. I've done it using a post in stackoverflow. It's like the following.
+(UIImage *)addText:(UIImage *)img text:(NSString *)text1{
int w = img.size.width;
int h = img.size.height;
//lon = h - lon;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
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, "Arial", 18, kCGEncodingMacRoman);
CGContextSetTextDrawingMode(context, kCGTextFill);
CGContextSetRGBFillColor(context, 255, 255, 255, 1);
//rotate text
CGContextSetTextMatrix(context, CGAffineTransformMakeRotation( -M_PI/4 ));
CGContextShowTextAtPoint(context, 4, 52, text, strlen(text));
CGImageRef imageMasked = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return [UIImage imageWithCGImage:imageMasked];
}
When I'm writing a text using this code, the original image's colour is changed like the following,
Original Image
Output with Text
Can anyone explain why is this happening. and how to fix this??
Thanks in Advance!!

Answer 1

We need to create a image context and apply drawing and get final image from this context. You can try this method. Hope this help you.
+ (UIImage *) addText:(UIImage *)img text:(NSString *)text
{
CGRect rect = [[UIScreen mainScreen] bounds];
// create a context according to image size
UIGraphicsBeginImageContext(rect.size);
// draw image
[img drawInRect:rect];
UIFont* font = [UIFont systemFontOfSize:14.0];
/// Make a copy of the default paragraph style
NSMutableParagraphStyle* paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
/// Set line break mode
paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;
/// Set text alignment
paragraphStyle.alignment = NSTextAlignmentCenter;
NSDictionary *attributes = #{ NSFontAttributeName: font,
NSParagraphStyleAttributeName: paragraphStyle };
CGRect textRect = CGRectMake(20, 160.0, 280.0, 44);
/// draw text
[text drawInRect:textRect withAttributes:attributes];
// get as image
UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}

Answer 2

EDIT: This can only be run on the main thread! So it's pretty much useless.
+(UIImage *)imageFromView:(UIView *)view
{
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
Here's a new one using Core Graphics that can be used on any thread
+ (UIImage *)imageFromView:(UIView *)view
{
size_t width = view.bounds.size.width*2;
size_t height = view.bounds.size.height*2;
unsigned char *imageBuffer = (unsigned char *)malloc(width*height*8);
CGColorSpaceRef colourSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef imageContext = CGBitmapContextCreate(imageBuffer, width, height, 8, width*4, colourSpace,kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colourSpace);
CGContextTranslateCTM(imageContext, 0.0, height);
CGContextScaleCTM(imageContext, 2.0, -2.0);
[view.layer renderInContext:imageContext];
CGImageRef outputImage = CGBitmapContextCreateImage(imageContext);
UIImage *image = [[UIImage alloc] initWithCGImage:outputImage];
CGImageRelease(outputImage);
CGContextRelease(imageContext);
free(imageBuffer);
return image;
}

Answer 3

I am using this and it works fine for me
- (UIImage*) drawText:(NSString*) text
inImage:(UIImage*) image
atPoint:(CGPoint) point
{
UIFont *font = [UIFont fontWithName:FONT_BOLD size:20];
UIGraphicsBeginImageContext(image.size);
[image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];
CGRect rect = CGRectMake(point.x, point.y, image.size.width, image.size.height);
[UIColorFromRGB(0x515151) set];
[text drawInRect:CGRectIntegral(rect) withFont:font];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}