I am trying for a image relaterd i-phone application.I am using a line of code
CGContextDrawImage(context1, CGRectMake(0, 0, width, height), imageRef);
I am working with multiple images.So i want to clear the screen after this .Any built in function using for this (Like in C we can use cleardevice in graphics).Any help appreciating.
Check out CGContextFillRect - just set the rect to be the whole view and the brush to be solid white :)
For example, to clear the image you just drew with white :
const CGFloat white[] = {1.0f, 1.0f, 1.0f, 1.0f};
CGContextSetFillColor(context1, white);
CGContextFillRect(context1, CGRectMake(0, 0, width, hight));
Related
So I have the following code:
CGContextDrawImage(context, CGRectMake(100, 0, 220, self.image.size.height), self.image.CGImage);
basically I am asking CG to draw the image 100 px to the right.. now this works fine.. however to the left of the image I see a white background. How do I change this background to some other color? Say I want a black blackground
Before drawing the image, fill the rect with the desired color:
CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
CGContextFillRect(context, CGRectMake(0, 0, self.image.size.width + 100, self.image.size.height)); //I suppose your rect's width is as much as image's width +100
//Then draw your image
CGContextDrawImage(context, CGRectMake(100, 0, 220, self.image.size.height), self.image.CGImage);
Note: Make sure the rect's you're drawing into width is at least the image's width + 100
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.
When I use UIImagePickerController with cameraOverlayView, can I get the only a selective region from my overlay view?
http://tinyurl.com/2fqy9nq
Add an UIImageView as child to your cameraOverlayView.
Create a black PNG image size 320x480. Cut a rectangle in the middle to produce a hole (transparent pixels).
Assign the PNG image to the UIImageView.
Alternatively you could overwrite your cameraOverlayView's - (void)drawRect:(CGRect)rect like this (untested out of my head):
// Request draw context
CGContextRef context = UIGraphicsGetCurrentContext();
// Draw background
CGContextSetRGBFillColor(context, 0.0f, 0.0f, 0.0f, 1.0f);
CGContextFillRect(context, rect);
// Cut hole
CGContextSetBlendMode(context, kCGBlendModeClear);
CGContextFillRect(context, CGRectMake(40, 40, 100, 100);
I have done something similar in my Faces app (http://faces.pixelshed.net/). Feel free to write a comment if one of the steps seems unclear.
i have a view with uiimageview i assign this uiimageview image by camera..now i want to do some drawing onto image....using coregraphics.i want to do something like this... select an area by touching and drawing line when line joins something like circle or any shape..i want to change that particular area in to something else for example change color there.turn that into grayscale.. till now i am able to draw line...here is an image of line drawn over a uiimage view...
but i am unable to figure it out how do i draw at imageview's image..mean how to modify imageview's image???
also i want to restore image when click on clear button or something like undo..does someone knows how to achieve this?
and
how do i create a rectangle when click on crop button move the rectangle any where on the screen...and then push the button to crop the image...and then save cropped image..
These are the steps:
Create a CGBitmapContext matching the image's colorspace and dimensions.
Draw the image into that context.
Draw whatever you want on top of the image.
Create a new image from the context.
Dispose off the context.
Here's a method that takes an image, draws something on top of it and returns a new UIImage with modified contents:
- (UIImage*)modifiedImageWithImage:(UIImage*)uiImage
{
// build context to draw in
CGImageRef image = uiImage.CGImage;
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGContextRef ctx = CGBitmapContextCreate(NULL,
CGImageGetWidth(image), CGImageGetHeight(image),
8, CGImageGetWidth(image) * 4,
colorspace, kCGImageAlphaPremultipliedLast);
CGColorSpaceRelease(colorspace);
// draw original image
CGRect r = CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image));
CGContextSetBlendMode(ctx, kCGBlendModeCopy);
CGContextDrawImage(ctx, r, image);
CGContextSetBlendMode(ctx, kCGBlendModeNormal);
// draw something
CGContextAddEllipseInRect(ctx, CGRectInset(r, 10, 10));
CGContextSetRGBStrokeColor(ctx, 1.0f, 1.0f, 1.0f, 0.5f);
CGContextSetLineWidth(ctx, 16.0f);
CGContextDrawPath(ctx, kCGPathStroke);
CGContextAddEllipseInRect(ctx, CGRectInset(r, 10, 10));
CGContextSetRGBStrokeColor(ctx, 0.7f, 0.0f, 0.0f, 1.0f);
CGContextSetLineWidth(ctx, 4.0f);
CGContextDrawPath(ctx, kCGPathStroke);
// create resulting image
image = CGBitmapContextCreateImage(ctx);
UIImage* newImage = [[[UIImage alloc] initWithCGImage:image] autorelease];
CGImageRelease(image);
CGContextRelease(ctx);
return newImage;
}
To restore to old image, just keep a reference to it.
The cropping thing is not related to the above and you should create a new question for that.
A lot easier solution would be
(UIImage *) modifyImage:(UIImage *)inputImage
{
UIGraphicsBeginImageContext(inputImage.size);
[inputImage drawInRect:CGRectMake(0, 0, inputImage.size.width, inputImage.size.height);
CGContextRef ctx = UIGraphicsGetCurrentContext();
//Drawing code using above context goes here
/*
*
*/
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage;
}
Take a look at Overview of Quartz 2D for information on using Quartz 2D on iPhone.
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.