I have imageA (taken from the users iPhone camera) and imageB, an image with a silly boarder (for eg) with plenty of transparent alpha space.
What I would like to to do is to merge these two images, laying imageB over imageA, and then saving them as imageC for other work.
Is there a way to do this?
Cheers
I've got this so far
-(void)merge
{
CGSize size = CGSizeMake(320, 480);
UIGraphicsBeginImageContext(size);
CGPoint thumbPoint = CGPointMake(0,0);
UIImage *imageA = imageView.image;
[imageA drawAtPoint:thumbPoint];
UIImage* starred = [UIImage imageNamed:#"imageB.png"];
CGPoint starredPoint = CGPointMake(0, 0);
[starred drawAtPoint:starredPoint];
UIImage *imageC = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
imageView.image = imageC;
}
I can't see/dont know what I'm doing wrong here
That code looks correct (though I would recommend converting it to use a created CGBitmapContext for thread-safety), but is imageB supposed to be a JPEG? JPEGs don't support transparency, so, in order for the blending to work, it should really be a PNG.
Note that for retina support you should use: UIGraphicsBeginImageContextWithOptions(size, YES, 0); // 0 means let iOS deal with scale for you
Related
I have a CALayer with an image in it, and it has several sublayers. I want to animate it to have no contents (no image), but continue showing the sublayers. This code does not work:
CABasicAnimation *backgroundOut = [CABasicAnimation animationWithKeyPath:#"contents"];
backgroundOut.toValue = [NSNull null];
backgroundOut.fillMode = kCAFillModeForwards;
backgroundOut.removedOnCompletion = NO;
backgroundOut.duration = 3.0;
[_backgroundLayer addAnimation:backgroundOut forKey:#"contents"];
Here is the only way I could get this to work:
backgroundOut.toValue = (__bridge id)([UIImage imageNamed:#"blankImage"].CGImage);
Note that I don't want to mess with the opacity or anything because this layer has sublayers that need to still be visible.
What is the proper way to animate to empty contents?
I decided this was the cleanest approach, since there was no other answer forthcoming:
UIGraphicsBeginImageContextWithOptions(CGSizeMake(1, 1), NO, 0);
UIImage *blank = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CABasicAnimation *backgroundOut = [CABasicAnimation animationWithKeyPath:#"contents"];
backgroundOut.toValue = (__bridge id)(blank.CGImage);
backgroundOut.fillMode = kCAFillModeForwards;
backgroundOut.removedOnCompletion = NO;
backgroundOut.duration = 3.0;
[_backgroundLayer addAnimation:backgroundOut forKey:#"contents"];
Another approach might be to create a separate layer to contain your image that is a peer of your other layers, but just behind the other layers (you can use zposition to place it behind the other layers explicitly)--all contained within a root layer. Then, you can animate the image layer's alpha for a fade and won't have the overhead of creating an image on the fly and it won't then fade the other layers.
I wish to overlay one CGImage over another.
As an example the first CGImage is 1024x768 and want to overlay a second 100x100 CGImage at a given location.
I have seen how to do this using NSImage but don't really want to convert my CGImages to NSImage's then do overlay then convert the result back to CGImage. I have also seen iOS versions of the code, but unsure how to go about it on Mac?
I'm mostly used to iOS, so I might be out of my depth here, but assuming you have a graphics context (sized like the larger of the two images), can't you just draw the two CGImages on top of each other?
CGImageRef img1024x768;
CGImageRef img100x100;
CGSize imgSize = CGSizeMake(CGImageGetWidth(img1024x768), CGImageGetHeight(img1024x768));
CGRect largeBounds = CGRectMake(0, 0, CGImageGetWidth(img1024x768), CGImageGetHeight(img1024x768));
CGContextDrawImage(ctx, largeBounds, img1024x768);
CGRect smallBounds = CGRectMake(0, 0, CGImageGetWidth(img100x100), CGImageGetHeight(img100x100));
CGContextDrawImage(ctx, smallBounds, img100x100);
And then draw the result into a NSImage?
This is my image resize code:
CALayer *newCALayer = [[CALayer layer] retain];
NSImage* image = [[NSImage alloc] initWithData:[NSData dataWithContentsOfFile:path]];
CGImageRef newCGImageFullResolution = [image CGImageForProposedRect:nil context:nil hints:nil];
CGContextRef context = CGBitmapContextCreate(NULL, drawRect.size.width, drawRect.size.height,
CGImageGetBitsPerComponent(newCGImageFullResolution),
CGImageGetBytesPerRow(newCGImageFullResolution),
CGImageGetColorSpace(newCGImageFullResolution),
CGImageGetAlphaInfo(newCGImageFullResolution));
CGContextDrawImage(context, CGRectMake(0, 0, drawRect.size.width, drawRect.size.height), newCGImageFullResolution);
CGImageRef scaledImage = CGBitmapContextCreateImage(context);
newCALayer.contents = (id)scaledImage;
CGImageRelease(scaledImage);
newCALayer.contentsGravity = kCAGravityResizeAspect;
newCALayer.opacity = 0.0;
newCALayer.anchorPoint = CGPointMake(0.0f,0.0f);
newCALayer.frame = CGRectMake( 0.0,
0.0,
[Singleton sharedSingleton].fullscreenRect.size.width,
[Singleton sharedSingleton].fullscreenRect.size.height);
[newCALayer setAutoresizingMask:kCALayerWidthSizable | kCALayerHeightSizable];
//CGImageRelease(cgImageFullResolution); (bonus points if you can explain why I can't release this! I mean, I can release the scaled image ok??)
CGContextRelease(context);
[image release];
I am doing all of this from a background thread in order to preload pictures so my GUI feels snappy. It took some work getting synchronization and what not set up so the CALayers ends up in view.
But I believe the term for describing how fast this is would be "it's a dog".
Comparing to IKImageView - that thing flings up thumbnails of images faster than I can scroll.
Does anybody have some suggestions for how to handle this better than I am doing it now?
In other words, my problem is that I want to have a super-fast UX. I believe the way to accomplish this is by preloading things to CALayers (this may be wrong? I tried NSImageView and some IK-stuff, but at least CALayer is better than that).
ImageKit is probably using CGImageSourceCreateThumbnailAtIndex() to quickly get an image appropriate to the destination, rather than reading in the entire image file.
Here:
NSImage *image = [[[NSImage alloc] initWithContentsOfFile:path] autorelease];
[image setScalesWhenResized:YES]; // *
[image setDataRetained:YES]; // *
[image setSize:desiredNewSize];
Then use the image as it is.
As for why your app is slow, run it under Instruments. That will tell you specifically where you are spending the majority of the processor time you use—it may not be in your scaling code after all.
*Since 10.6, these messages do nothing useful and are deprecated, so you can omit them if you are requiring Snow Leopard or later.
I'm writing a QuickLook plugin. Well, everything works. Just want to try it make better ;).
Thus the question.
Here is a function that returns thumbnail image and that I'm using now.
QLThumbnailRequestSetImageWithData(
QLThumbnailRequestRef thumbnail,
CFDataRef data,
CFDictionaryRef properties);
);
http://developer.apple.com/mac/library/documentation/UserExperience/Reference/QLThumbnailRequest_Ref/Reference/reference.html#//apple_ref/c/func/QLThumbnailRequestSetImageWithData
Right now I'm creating a TIFF -> encapsulated it into NSData. An example
// Setting CFDataRef
CGSize thumbnailMaxSize = QLThumbnailRequestGetMaximumSize(thumbnail);
NSMutableAttributedString *attributedString = [[[NSMutableAttributedString alloc]
initWithString:#"dummy"
attributes:[NSDictionary dictionaryWithObjectsAndKeys:
[NSFont fontWithName:#"Monaco" size:10], NSFontAttributeName,
[NSColor colorWithCalibratedRed:0.0 green:0.0 blue:0.0 alpha:1.0], NSForegroundColorAttributeName,
nil]
] autorelease];
NSImage *thumbnailImage = [[[NSImage alloc] initWithSize:NSMakeSize(thumbnailMaxSize.width, thumbnailMaxSize.height)] autorelease];
[thumbnailImage lockFocus];
[[NSColor whiteColor] set];
NSRectFill(NSMakeRect(0, 0, thumbnailMaxSize.width, thumbnailMaxSize.height));
[attributedString drawInRect:NSMakeRect(0, 0, thumbnailMaxSize.width, thumbnailMaxSize.height)];
[thumbnailImage unlockFocus];
(CFDataRef)[thumbnailImage TIFFRepresentation]; // This is data
// Setting CFDictionaryRef
(CFDictionaryRef)[NSDictionary dictionaryWithObjectsAndKeys:#"kUTTypeTIFF", (NSString *)kCGImageSourceTypeIdentifierHint, nil ]; // this is properties
However QuickLook provides another function to return thumbnail image, namely
QLThumbnailRequestSetImage(
QLThumbnailRequestRef thumbnail,
CGImageRef image,
CFDictionaryRef properties);
);
http://developer.apple.com/mac/library/documentation/UserExperience/Reference/QLThumbnailRequest_Ref/Reference/reference.html#//apple_ref/c/func/QLThumbnailRequestSetImage
I have a feeling that passing CGImage to the QL instead of TIFF data would help in speeding things up.
However- I have never worked with CG context before. I know, the documentation is there :), but anyways- could anyone give an example how to turn that NSAttributed string into CGImageRef. An example is worth 10 times reading the documentation ;)
Any help appreciated. Thanks in advance!
could anyone give an example how to turn that NSAttributed string into CGImageRef.
You can't turn a string into an image; they're two completely different kinds of data, and one is two dimensional (characters over time) while the other is at-least-three dimensional (color over x and y).
What you need to do is draw the string and produce an image of the drawing. That's what you're doing now with NSImage: Creating an image and drawing the string into it.
You're asking about creating a CGImage. Creating a bitmap context, using Core Text to draw the string into it, and creating an image of the contents of the bitmap context is one way to do that.
However, you're already much closer to another solution, assuming you can require Snow Leopard. Instead of asking the NSImage for a TIFF representation, ask it for a CGImage.
Summary: exporting pixel data from NSOpenGLView to some file formats gives incorrect colours
I am developing an application to visualise some experimental data. One of its functions is to render the data in an NSOpenGLView subclass, and allow the resulting image to be exported to a file or copied to the clipboard.
The view exports the data as an NSImage, generated like this:
- (NSImage*) image
{
NSBitmapImageRep* imageRep;
NSImage* image;
NSSize viewSize = [self bounds].size;
int width = viewSize.width;
int height = viewSize.height;
[self lockFocus];
[self drawRect:[self bounds]];
[self unlockFocus];
imageRep=[[[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
pixelsWide:width
pixelsHigh:height
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSDeviceRGBColorSpace
bytesPerRow:width*4
bitsPerPixel:32] autorelease];
[[self openGLContext] makeCurrentContext];
glReadPixels(0,0,width,height,GL_RGBA,GL_UNSIGNED_BYTE,[imageRep bitmapData]);
image=[[[NSImage alloc] initWithSize:NSMakeSize(width,height)] autorelease];
[image addRepresentation:imageRep];
[image setFlipped:YES]; // this is deprecated in 10.6
[image lockFocusOnRepresentation:imageRep]; // this will flip the rep
[image unlockFocus];
return image;
}
Copying uses this image very simply, like this:
- (IBAction) copy:(id) sender
{
NSImage* img = [self image];
NSPasteboard* pb = [NSPasteboard generalPasteboard];
[pb clearContents];
NSArray* copied = [NSArray arrayWithObject:img];
[pb writeObjects:copied];
}
For file writing, I use the ImageKit IKSaveOptions accessory panel to set the output file type and associated options, then use the following code to do the writing:
NSImage* glImage = [glView image];
NSRect rect = [glView bounds];
rect.origin.x = rect.origin.y = 0;
img = [glImage CGImageForProposedRect:&rect
context:[NSGraphicsContext currentContext]
hints:nil];
if (img)
{
NSURL* url = [NSURL fileURLWithPath: path];
CGImageDestinationRef dest = CGImageDestinationCreateWithURL((CFURLRef)url,
(CFStringRef)newUTType,
1,
NULL);
if (dest)
{
CGImageDestinationAddImage(dest,
img,
(CFDictionaryRef)[imgSaveOptions imageProperties]);
CGImageDestinationFinalize(dest);
CFRelease(dest);
}
}
(I've trimmed a bit of extraneous code here, but nothing that would affect the outcome as far as I can see. The newUTType comes from the IKSaveOptions panel.)
This works fine when the file is exported as GIF, JPEG, PNG, PSD or TIFF, but exporting to PDF, BMP, TGA, ICNS and JPEG-2000 produces a red colour artefact on part of the image. Example images are below, the first exported as JPG, the second as PDF.
(source: walkytalky.net)
(source: walkytalky.net)
Copy to clipboard does not exhibit this red stripe with the current implementation of image, but it did with the original implementation, which generated the imageRep using NSCalibratedRGBColorSpace rather than NSDeviceRGBColorSpace. So I'm guessing there's some issue with the colour representation in the pixels I get from OpenGL that doesn't get through the subsequent conversions properly, but I'm at a loss as to what to do about it.
So, can anyone tell me (i) what is causing this, and (ii) how can I make it go away? I don't care so much about all of the formats but I'd really like at least PDF to work.
OK. As evidenced by the deafening silence which met this question, the problem turns out to be a bit obscure. But the workaround is nice and simple, so I'm describing it here just in case anyone ever wants to know.
Summary: some file export formats do not cope well with translucency in the rendered pixels.
I don't understand the exact reasons for this, although it might possibly have something to do with the presence or absence of alpha pre-multiplication. All the formats seem to be fine with completely transparent pixels, rendering them either transparent or as white if the format doesn't support transparency. But pixels that have a partial alpha, plus something in the colour channels, may get mangled.
As it happens, I did not even want any parts of the image to be translucent, and indeed set glDisable(GL_BLEND) before the relevant rendering code. However, objects were rendered with the materials from this seemingly-canonical collection at the OpenGL home site, some of which include alpha values other than 1.0 in their specular, diffuse and ambient colours. I had slavishly copied this without paying attention to that fact that it might lead to some unwanted translucency.
For my purposes, then, the solution is straightforward: change the material definitions so that the alpha component is always 1.0.
Note that some image formats, such as PNG and TIFF, do fully support the translucency, so if you need that then those are the ones to go for.
This was, in fact what tipped me off to the answer. However it was not obvious at first because I was using OS X Preview to view the files, and the translucency is not obvious with the default view settings:
(source: walkytalky.net)
(source: walkytalky.net)
(source: walkytalky.net)
(source: walkytalky.net)
So, a second lesson from this whole episode is: enable View | Show Image Background in Preview to get the checkerboard and show up any stray transparency.