I have some images and I want to draw them using drawAtPoint ( I am using a table of 100s of cells and doing the draw as recommended for making the scrolling faster). Now, these images are kind of random (their size can be anything.. ) and I need to specify the dimension I want to fit in.
Can anyone kindly tell me what to do ?
Thanks.
Assuming I understand what you want to do use:
- (void)drawInRect:(CGRect)rect;
See http://developer.apple.com/library/ios/#documentation/uikit/reference/UIImage_Class/Reference/Reference.html
When using drawAtPoint you cannot specify the dimensions, it will draw the entire image in the current graphics context.
Related
I'm trying to create an iOS recoloring app (this is my reference), and i need to know how recolor some portion of the image when user taps on a given area. All the loaded pictures will be black/white initially.
Is there any prebuilt library? Or which graphics framework should i use?
Any help will be appreciated.
If what you are looking for is adding/replacing the colour within a certain shape and edges are really important (as in the example) then you should be looking into vectorised drawing.
What this means is every shape in your image would have an actual object representation in your code, and you could easily interact with that object to do whatever you want (i.e. tap gestures to change colour, zoom etc.).
This however, means that you can't simply use .jpeg images, and you need to use images in vector format, such as .svg or CorelDraw.
As a reference, check out SVGKit, which is an excellent library for working with SVG images.
I need to create button like this
and the change the background programmatically like this
and like this
I can not use images for different states of a button because each time I have different text on it.
What to start from ? I tried to understand CoreGraphics and CoreAnimation but there is too small amount of examples and tutorials so my attempts didn't give me any success.
You can, and should, use an image for this. UIKit has a method resizableImageWithCapInsets that creates resizable images. You feed it a minimum sized image and the system stretches it to fit the desired size. It looks like your image is fixed in height, which is good since you can't do smooth gradients with this technique.
UIButtons are composed of a background image and title text, so you can use an image for the background shapes (setBackgroundImage(_:forState:)), and then change the text using setTitle(_:forState:).
However, you can still use Core Graphics for this, and there are benefits to doing so, such as the fact that it reduces the number of rendered assets in your app bundle. For this, probably the best approach is to create a CAShapeLayer with a path constructed from a UIBezierPath, and then render it into a graphics context. From this context, you can pull out a UIImage instance, and treat it just the same as an image loaded from a JPEG or PNG asset (that is, set it as the buttons background image using setBackgroundImage(_:forState:)).
I have two image views. They are "puzzle pieces" I want to test if one fits inside the other. Not that the frames overlap. I guess its a CGRect thing... but seems like they test the outer boundaries. Any ideas would be appreciated? Thanks.
Just brainstorming here... Maybe this will get you thinking of something that will work for you. If the images do not overlap, then drawing image A on top of image B will result in the same image as drawing image B on top of image A. If they overlap, that will result in different images. You could do something like draw image A, then B. Create a checksum of the result, draw A again, and checksum that. If the checksums match, the puzzle piece fits.
If you have a 1-bit mask that represents each image, then ORing them together and XORing them together will have the same result if they don't overlap and different results if they do.
Do you know the correct order of pieces beforehand? May be it's better assign the tag to each UIImageView which will represent the image's index number. Then you just create a kind of mesh and check in which cell the piece was placed. If the cell number and UIImageView tag match - then this is the right place.
If you have only two images and one must fit to the specific area in another, you could store the frame of this hole and check if the piece is placed somewhere around the centre of this frame. It'll be more user-friendly because when you're checking pixels or bit masks you want the user be extremely precise. Or your comparison code should allow some shifts and will be very complicated.
But if you don't want to hardcode the hole frame you could calculate it dynamically (just find transparent areas in the image). Anyway, this solution will be more effective then checking bit match on the fly.
I have two images that I want to display on top of each other. one image a single channel image and the second image is a RGB image but with most of the area being transparent.
How these two images are generated in different functions. I know to just display these on top of each other, i can use the same window name when calling cvShowImage() but this doesn't work when they are drawn from different functions. When trying this, I used cvCvtcolor() to convert he binary image from single channel to RGB and then displaying the second image from another function. But this didn't work. Both images are same dimension, depth and number of channels (after conversion).
I want to avoid passing in one image into the second function and then draw them. So I'm looking for a quick dirty trick to display these two images overlapped.
Thank you
EDIT:
I don't think that's possible. You'll have to create a new image or modify an existing one. Here's an article that shows how to do this: Transparent image overlays in OpenCV
There is no way to "overlay" images. cvShowImage() displays a single image from memory. You'll need to blend/combine them together. There are several ways to do this.
You can copy one into 1 or 2 channels of the other, you can use logical operations like AND, OR or XOR, you can use arithmetic operations like Add, Multiply and MultiplyScale (these operations will saturate values larger than 255). All these can also be done with an optional mask image like your blob image.
Naturally, you may want to do this into a third buffer so as not to overwrite your originals.
Apparently now it can be done using OpenCV 2.1 version
http://opencv.willowgarage.com/documentation/cpp/highgui_qt_new_functions.html#cv-displayoverlay
If I have a texture file how would I be able to load up only a part of it using a defined rect (top, left, bottom, right)?
Is it technically possibly to only read in the parts I want to load while leaving the rest of the texture untouched?
What exactly are you trying to achieve. Its pretty simple to load up only a small part of a file into a single texture that encompasses it all. You'll probably need to write your own image parser, though.
If you want to load a partial image into a texture thats the same size as the original image (ie only update the area you are after) then this is relaitvely simple as well. You can LockRcts with a rect that is the area you want you update. You'll still need to write your own image parser though.
Personally in situations like this I prefer to use my own texture format that is already in the format I'm after ...
Look at D3DXCreateTextureFromFileEx: http://msdn.microsoft.com/en-us/library/bb172802%28v=VS.85%29.aspx
Otherwise, load the portion of the data you require yourself into memory, create an empty texture and lock it and copy the data.