I'm trying to simply draw some text with a stroke and then apply a drop shaddow, but the stroke is being applied to drop shadow. How do I prevent this?
// Setup context
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
// draw photo into context
CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
// Set Text Font
CGContextSelectFont(context, font.fontName.UTF8String, fontSize, kCGEncodingMacRoman);
// Set Text Drawing Mode
CGContextSetTextDrawingMode(context, kCGTextFillStroke);
// Set text fill color
CGColorRef tmpColor = color.CGColor;
CGFloat newComponents[4] = {};
memcpy(newComponents, CGColorGetComponents(tmpColor), sizeof(newComponents));
CGContextSetRGBFillColor(context, newComponents[0], newComponents[1], newComponents[2], newComponents[3]);
// Calculate Height
UIFont *testFont = [UIFont fontWithName:font.fontName size:fontSize];
CGSize size = [text sizeWithFont:testFont];
// Setup Font Shadow
CGSize shadowSize = CGSizeMake(6, 6);
CGContextSetShadowWithColor(context, shadowSize, 1.0, [[UIColor darkGrayColor] CGColor]);
// Set Stroke Color
CGContextSetRGBStrokeColor(context, 0, 255, 0, 1);
CGContextSetLineWidth(context, 2.0);
// draw text at location centered based on width.
CGContextShowTextAtPoint(context, (w / 2) - (textWidth / 2), h - size.height, ctext, strlen(ctext));
// Render Bitmap
CGImageRef imageMasked = CGBitmapContextCreateImage(context);
UIImage *returnImage = [UIImage imageWithCGImage:imageMasked];
Because your text drawing mode is kCGTextFillStroke, CGContextShowTextAtPoint is first drawing the fill (and generating a shadow for it), and then drawing the stroke (which gets its own shadow).
To fix it, use a transparency layer.
Note that it will draw much faster if you use CGContextBeginTransparencyLayerWithRect() and pass in as small a rect as you can.
Alternatively: if it's a good enough approximation, you might consider drawing your text in two steps:
fill, with shadow
stroke, with no shadow
If your stroke is small, the difference will not be very perceptible, and it will draw considerably faster.
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'm currently drawing a line using Core Graphics. It's really bare bones and simple.
- (void)drawRect:(CGRect)rect {
CGContextRef c = UIGraphicsGetCurrentContext();
CGFloat red[4] = {1.0f, 0.0f, 0.0f, 1.0f};
CGContextSetStrokeColor(c, red);
CGContextBeginPath(c);
CGContextMoveToPoint(c, 5.0f, 5.0f);
CGContextAddLineToPoint(c, 300.0f, 600.0f);
CGContextSetLineWidth(c, 25);
CGContextSetLineCap(c, kCGLineCapRound);
CGContextStrokePath(c);
}
This works well. Let's say that we wanted to draw a custom style line. Say we wanted to imitate the style of a crayon for example. And that the designer handed your crayon style images: http://imgur.com/a/N40ig
To do accomplish this effect I think I need to do something like this:
Create a special colored versions of crayonImage1-crayonImage4
Every time you add a line to line you use one of the crayonImages
You alternate the crayonImages every time you draw a point.
Step 1 makes sense. I can use the following method:
- (UIImage *)image:(UIImage *)img withColor:(UIColor *)color {
// begin a new image context, to draw our colored image onto
UIGraphicsBeginImageContext(img.size);
// get a reference to that context we created
CGContextRef context = UIGraphicsGetCurrentContext();
// set the fill color
[color setFill];
// translate/flip the graphics context (for transforming from CG* coords to UI* coords
CGContextTranslateCTM(context, 0, img.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// set the blend mode to color burn, and the original image
CGContextSetBlendMode(context, kCGBlendModeColorBurn);
CGRect rect = CGRectMake(0, 0, img.size.width, img.size.height);
CGContextDrawImage(context, rect, img.CGImage);
// set a mask that matches the shape of the image, then draw (color burn) a colored rectangle
CGContextClipToMask(context, rect, img.CGImage);
CGContextAddRect(context, rect);
CGContextDrawPath(context,kCGPathFill);
// generate a new UIImage from the graphics context we drew onto
UIImage *coloredImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
//return the color-burned image
return coloredImg;
}
I'm unsure how I can complete steps 2 and 3. Is there an API in CoreGraphics for setting an image as the point of line? If so what is it and how can I use it?
Thanks in advance,
-David
Start with the following example: http://www.ifans.com/forums/showthread.php?t=132024
But for brushes, don't draw a line. Simply draw the brush image using CGContextDrawImage.
Basically, you simply draw an image for every touch.
I assume that the background is transparent automatically if I use the device color space (RGBA, so with alpha). But I'm not sure.
How can I set the background color of my drawing canvas or bitmap context explicitely to make sure it is transparent when it is created?
CGContextSetRGBFillColor(ctx, 0, 0, 0, 1); //black color
CGContextSetRGBFillColor(ctx, 0, 0, 0, 0); //transparent color - alpha set to null
CGContextSetRGBFillColor ( c red green blue alpha -- )
USING: alien.c-types alien.syntax core-graphics.types ;
IN: core-graphics
FUNCTION: void CGContextSetRGBFillColor ( CGContextRef c, CGFloat red, CGFloat green, CGFloat blue,CGFloat alpha ) ;
see more: http://oss.infoscience.co.jp/factor/docs.factorcode.org/content/word-CGContextSetRGBFillColor,core-graphics.html
This code will work fine.
// transparent
CGContextSetRGBFillColor(cacheContext, 0.0, 0.0, 0.0, 0.0);
// image
CGImageRef cgImage = [[UIImage imageNamed:#"img.png"] CGImage];
CGContextDrawImage(cacheContext, self.bounds, cgImage);
CGContextFillRect(cacheContext, self.bounds);
I'm trying to add a small shadow to an image, much like the icon shadows in the App Store. Right now I'm using the following code to round the corners of my images. Does anyone know how I can adapt it to add a small shadow?
- (UIImage *)roundCornersOfImage:(UIImage *)source height:(int)height width:(int)width {
int w = width;
int h = height;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef imageContext = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
CGContextBeginPath(imageContext);
CGRect rect = CGRectMake(0, 0, w, h);
addRoundedRectToPath(imageContext, rect, 10, 10);
CGContextClosePath(imageContext);
CGContextClip(imageContext);
CGContextDrawImage(imageContext, CGRectMake(0, 0, w, h), source.CGImage);
CGImageRef imageMasked = CGBitmapContextCreateImage(imageContext);
CGContextRelease(imageContext);
CGColorSpaceRelease(colorSpace);
return [UIImage imageWithCGImage:imageMasked];
}
addRoundedRectToPath refers to another method that obviously rounds the corners.
First, here's a link to the documentation:
http://developer.apple.com/iPhone/library/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_shadows/dq_shadows.html#//apple_ref/doc/uid/TP30001066-CH208-TPXREF101
Next, try adding something like this right before the call to CGContextDrawImage(...):
CGFloat components[4] = {0.0, 0.0, 0.0, 1.0};
CGColorRef shadowColor = CGColorCreate(colorSpace, components);
CGContextSetShadowWithColor(imageContext, CGSizeMake(3, 3), 2, shadowColor);
CGColorRelease(shadowColor);
After, the call to CGContextSetShadowWithColor(.....), everything should draw with a shadow that is offset by (3, 3) points, and drawn with a 2.0 point blur radius. You'll probably want to tweak the opacity of the black color (the forth component in components), and change the shadow parameters.
If you'd like to stop drawing with a shadow at some point, you need to save the graphics context before calling CGContextSetShadowWithColor, and restore it when you want to stop drawing with a shadow.
I try to draw a string in this texture:
http://picasaweb.google.it/lh/photo/LkYWBv_S_9v2d6BAfbrhag?feat=directlink
but the green numbers seem vertical flipped.
I've created my context in this way:
colorSpace = CGColorSpaceCreateDeviceRGB();
data = malloc(height * width * 4);
context = CGBitmapContextCreate(data, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
and i've draw the strings:
UIGraphicsPushContext(context);
for(int i=0;i<packs.size();++i)
{
CGPoint points[4] =
{
gltextures[i].texCoords[0] * size.width, //0
gltextures[i].texCoords[1] * size.height, //1
gltextures[i].texCoords[2] * size.width, //2
gltextures[i].texCoords[3] * size.height, //3
gltextures[i].texCoords[4] * size.width, //4
gltextures[i].texCoords[5] * size.height, //5
gltextures[i].texCoords[6] * size.width, //6
gltextures[i].texCoords[7] * size.height //7
};
CGRect debugRect = CGRectMake
(
gltextures[i].texCoords[0] * size.width,
gltextures[i].texCoords[1] * size.height,
gltextures[i].width,
gltextures[i].height
);
CGContextSetStrokeColorWithColor(context, [[UIColor redColor] CGColor]);
CGContextAddLines(context, points, 4);
CGContextClosePath(context);
CGContextDrawPath(context, kCGPathStroke);
NSString* s = [NSString stringWithFormat:#"%d",gltextures[i].texID];
UIFont* font = [UIFont fontWithName:#"Arial" size:12];
CGContextSetRGBFillColor(context, 0, 1, 0, 1);
[s drawAtPoint:points[0] withFont:font];
}
UIGraphicsPopContext();
The transformation matrix seems the Identity matrix... no CGAffineTransform is applied to THIS context.
If the string is flipped, maybe, all my images are flipped!
Any suggestion?
PS: sorry for my english ;)
As describe here, the coordinate system for a context within a UIView or its layer is inverted when compared to the normal Quartz drawing space. However, when using Quartz to draw to an image, this is no longer the case. The UIStringDrawing Cocoa Touch category on NSString that gives you the -drawAtPoint:withFont: method assumes an inverted layout, and that's why you're seeing the flipped text in your image.
One way to work around this would be to save the graphics state, apply an invert transform to the image, draw the text, and restore the old graphics state. This would look something like the following:
CGContextSaveGState(context);
CGContextTranslateCTM(context, 0.0f, self.bounds.size.height);
CGContextScaleCTM(context, 1.0f, -1.0f);
[text drawAtPoint:CGPointMake(0.0f, 0.0f) withFont:font];
CGContextRestoreGState(context);
This is a fairly crude example, in that I believe it just draws the text at the bottom of the image, but you should be able to adjust the translation or the coordinate of the text to place it where it's needed.
Better save the text 's matrix before draw, otherwise it will affect other text draw by CoreGraphic:
CGContextSaveGState(ctx);
CGAffineTransform save = CGContextGetTextMatrix(ctx);
CGContextTranslateCTM(ctx, 0.0f, self.bounds.size.height);
CGContextScaleCTM(ctx, 1.0f, -1.0f);
[str drawAtPoint:point withFont:font];
CGContextSetTextMatrix(ctx, save);
CGContextRestoreGState(ctx);