I am having trouble drawing my imageView.image in the correct position using drawAtPoint. In the app I have used CGAffineTransformMakeRotation to rotate the image view, but when I want to save the imageView as part of a merge with others using UIGraphicsGetImageFromCurrentImageContext I don't know how to tell it to rotate.. all I am doing is rotating 180 degrees. here is the code I am using to merge it with another image.
UIGraphicsBeginImageContext(imageView.bounds.size);
[imageView.image drawAtPoint:CGPointMake(-40,0)];
[topView.image drawAtPoint:CGPointMake(0,160)];
UIImage *mergedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
So my question is: How do I drawAtPoint with rotation of 180 degrees or 3.14159265 radians?
Thanks in advance.
You can apply a transform to the image content, so all subsequent painting operation will be drawn with that transform, e.g. (untested)
UIGraphicsBeginImageContext(size);
CGContextRef c = UIGraphicsGetCurrentContext();
CGContextRotateCTM(c, M_PI/6);
[image drawAtPoint:CGPointZero];
...
Related
I have a UIImageView with is filled with image either taken by camera or picked from the liabray after I assign UIImage to UIImageView I want to rotate it with either clockwise or anticlock wise using 2 button respectively for both on every click image should rotate but without rotationg in superview UIImageView then after I want so save the image in the final position user saved that image...
If there is any method or procedure then please share as i m searching on this query from last many days but not got any acurate solution with proper details and working.
Rotation routine ( found this routine on another post but I forget where):
-(UIImage *)rotateImage:(UIImage *)image angleInRadians:(float)angleInRadians {
UIGraphicsBeginImageContext(image.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextRotateCTM(ctx, angleInRadians);
CGContextDrawImage(ctx, (CGRect){{}, image.size}, image);
UIImage *imageOut = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return imageOut;
}
Angle in raadians could be M_PI/2 or -M_PI/2 to change landscape to portrait or viceversa
UIGraphicsBeginImageContext(backgroundImageView.frame.size);
UIImageView *image1 = backgroundImageView;
UIImageView *image2 = boat;
// Draw image1
[image1.image drawInRect:CGRectMake(0, 0, image1.image.size.width, image1.image.size.height)];
// Draw image2
[image2.image drawInRect:CGRectMake(boat.center.x, boat.center.y, boat.image.size.width, boat.image.size.height)];
UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
When resultingImage is displayed the transform angle value for image2 is not preserved after I set it equal to the boat UIImageView. I thought that when I set image2 = boat that the transform value of boat would carry over to image2.
I suspect it relates to the fact that I am I am working with UIImageView instead of UIVIew. I have tried many different things but have been unable to resolve this issue.
Any help would be appreciated.
Thanks.
When you draw an image into a graphics context, it uses the context's transformation matrix, which is distinct from any transformation applied to a view. So the transformation on image2 (a UIImageView presumably) is completely irrelevant to direct image drawing.
You can either specify a new transformation with the various CGContext and CGAffineTransform functions in Quartz, or you can directly apply a copy of the UIImageView 's transformation like so:
CGContextConcatCTM(UIGraphicsGetCurrentContext(), someView.transform);
[someView.image drawInRect: CGRectMake(...)];
So I have a spritesheet in png format, and have already worked out the coordinates for what I want to display. I'm trying to create a method that will return a UIImage when passed the location information on the spritesheet. I'm just not sure how to use the CGContext stuff along with the the coordinates to return an UIImage.
I was looking to CGContextClipToRect because I think that is the way to do it, but I just can't seem to get it to work.
Something like this
CGSize size = CGSizeMake(xSize, ySize);
UIGraphicsBeginImageContext(size);
//CGContextClipToRect(spriteSheet.size, imageRect);
[spriteSheet drawAtPoint:CGPointMake(xPos, yPos)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
returns only what is in the size Context. I need to be able to "move" this size window around the spritesheet if that makes sense.
Any help would be appreciated.
Thanks,
Mike
I think the call you want to use is CGImageCreateWithImageInRect
newImage = [UIImage imageWithCGImage:CGImageCreateWithImageInRect( [spriteSheet CGImage] , imageRect )];
you need to think of your co-ordinates backwards. The CGSize is fixed. Translate your xPos,yPos so that your sprite appears under the window.
It's really a pain, but always when I draw an UIImage in -drawRect:, it's upside-down.
When I flip the coordinates, the image draws correctly, but at the cost of all other CG functions drawing "wrong" (flipped).
What's your strategy when you have to draw images and other things? Is there any rule of thumb how to not get stuck in this problem over and over again?
Also, one nasty thing when I flip the y-axis is, that my CGRect from the UIImageView frame is wrong. Instead of the origin appearing at 10,10 upper left as expected, it appears at the bottom.
But at the same time, all those normal line drawing functions of CGContext take correct coordinates. drawing a line in -drawRect with origin 10,10 upper left, will really start at upper left. But at the same time that's strange, because core graphics actually has a flipped coordinate system with y 0 at the bottom.
So it seems like something is really inconsistent there. Drawing with CGContext functions takes coordinates as "expected" (cmon, nobody thinks in coordinates starting from bottom left, that's silly), while drawing any kind of image still works the "wrong" way.
Do you use helper methods to draw images? Or is there anything useful that makes image drawing not a pain in the butt?
Problem: Origin is at lower-left corner; positive y goes upward (negative y goes downward).
Goal: Origin at upper-left corner; positive y going downward (negative y going upward).
Solution:
Move origin up by the view's height.
Negate (multiply by -1) the y axis.
The way to do this in code is to translate up by the view bounds' height and scale by (1, -1), in that order.
There are a couple of portions of the Quartz 2D Programming Guide that are relevant to this topic, including “Drawing to a Graphics Context on iPhone OS” and the whole chapter on Transforms. Of course, you really should read the whole thing.
You can do that by apply affinetransform on the point you want to convert in UIKit related coordinates. Following is example.
// Create a affine transform object
CGAffineTransform transform = CGAffineTransformMakeScale(1, -1);
// First translate your image View according to transform
transform = CGAffineTransformTranslate(transform, 0, - imageView.bounds.size.height);
// Then whenever you want any point according to UIKit related coordinates apply this transformation on the point or rect.
// To get tranformed point
CGPoint newPointForUIKit = CGPointApplyAffineTransform(oldPointInCGKit, transform);
// To get transformed rect
CGRect newRectForUIKit = CGRectApplyAffineTransform(oldPointInCGKit, transform);
The better answer to this problem is to use the UIImage method drawInRect: to draw your image. I'm assuming you want the image to span the entire bounds of your view. This is what you'd type in your drawRect: method.
Instead of:
CGContextRef ctx = UIGraphicsGetCurrentContext();
UIImage *myImage = [UIImage imageNamed:#"theImage.png"];
CGImageRef img = [myImage CGImage];
CGRect bounds = [self bounds];
CGContextDrawImage(ctx, bounds, img);
Write this:
UIImage *myImage = [UIImage imageNamed:#"theImage.png"];
CGRect bounds = [self bounds];
[myImage drawInRect:bounds];
It's really a pain, but always when I draw an UIImage in -drawRect:, it's upside-down.
Are you telling the UIImage to draw, or getting its CGImage and drawing that?
As noted in “Drawing to a Graphics Context on iPhone OS”, UIImages are aware of the difference in co-ordinate spaces and should draw themselves correctly without you having to flip your co-ordinate space yourself.
CGImageRef flip (CGImageRef im) {
CGSize sz = CGSizeMake(CGImageGetWidth(im), CGImageGetHeight(im));
UIGraphicsBeginImageContextWithOptions(sz, NO, 0);
CGContextDrawImage(UIGraphicsGetCurrentContext(),
CGRectMake(0, 0, sz.width, sz.height), im);
CGImageRef result = [UIGraphicsGetImageFromCurrentImageContext() CGImage];
UIGraphicsEndImageContext();
return result;
}
Call the above method using the code below:
This code deals with getting the left half of an image from an existing UIImageview and setting the thus generated image to a new imageview - imgViewleft
CGContextRef con = UIGraphicsGetCurrentContext();
CGContextDrawImage(con,
CGRectMake(0,0,sz.width/2.0,sz.height),
flip(leftReference));
imgViewLeft = [[UIImageView alloc] initWithImage:UIGraphicsGetImageFromCurrentImageContext()];
I've a problem with drawing images on PDF. I do apply scaling, rotation, move, etc. to an image and draws that image on the PDF. But drawing is not outputting correctly. When I do rotate image, it just scales and doesn't rotate.
Here, I explain in more detail:
I place an image on UIWebView to make fake effect of image exactly on PDF. Then, I do draw image on PDF which is on the UIWebView while making PDF.
But when I go and prepare PDF with modified image, which has been applied lots of transformations, image scales not rotates.
Here, img_copyright is a Custom class inheriting UIImageView.
CGFloat orgY = (newY-whiteSpace)+img_copyright.frame.size.height;
CGFloat modY = pageRect.size.height-orgY;
CGFloat orgX = img_copyright.frame.origin.x-PDF_PAGE_PADDING_WIDTH;
CGFloat modX = orgX;
//We're getting X,Y of the image here to decide where to put the image on PDF.
CGRect drawRect = CGRectMake (modX, modY, img_copyright.frame.size.width, img_copyright.frame.size.height);
//Preparing the rectangle in which image is to be drawn.
CGContextDrawImage(pdfContext, drawRect, [img_copyright.image CGImage]);
[img_copyright release];
// Actually drawing the image.
But when i see the PDF image is not properly drawn into it.
What would you suggest, is it the problem due to image drawing based on its X,Y?
How could we decide where to put the image on PDF if we don't depend on X, Y?
What is the exact method of drawing image on PDF with rotation, scale?
The Image when I do insert the image onto UIWebView's scrollbar.
http://www.freeimagehosting.net/">
The Image when I do draw the image onto PDF.
http://www.freeimagehosting.net/">
CGFloat angleInRadians =-1*Angle* (M_PI / 180.0);
CGAffineTransform transform=CGAffineTransformIdentity;
transform = CGAffineTransformMakeRotation(angleInRadians);
//transform = CGAffineTransformMakeScale(1, -1);
//transform =CGAffineTransformMakeTranslation(0,80);
CGRect rotatedRect = CGRectApplyAffineTransform(CGRectMake(0,0,Image.size.width,Image.size.height), transform);
UIGraphicsBeginImageContext(rotatedRect.size);
//[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), 0,rotatedRect.size.height);
CGContextScaleCTM(UIGraphicsGetCurrentContext(),1, -1);
//CGContextTranslateCTM(UIGraphicsGetCurrentContext(), +(rotatedRect.size.width/2),+(rotatedRect.size.height/2));
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), (rotatedRect.origin.x)*-1,(rotatedRect.origin.y)*-1);
CGContextRotateCTM(UIGraphicsGetCurrentContext(), angleInRadians);
//CGContextTranslateCTM(UIGraphicsGetCurrentContext(), -(rotatedRect.size.width/2),-(rotatedRect.size.height/2));
CGImageRef temp = [Image CGImage];
CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, Image.size.width,Image.size.height), temp);
//CGContextRotateCTM(UIGraphicsGetCurrentContext(), -angleInRadians);
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return viewImage;