How to draw a freehand drawing on UIView rather than UIImageView using touches moved method. I have many other subviews on this view so i cannot add image view as whole view.I have seen many examples but they are drawing in UIImageView.
see this sample .....
GLPaint Sample
You must use from their features. For lines, you just save two points on it, it is better to save its head and tail. For circle just save its center and radius. And For each points just save a pixel as a center. At the end of it, if your objects have some features as a color, thickness or ... just add these features inside of other features that I said.
I hope it be useful for you!
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I have been able to get the behavior I want using Xcode and the Attributes Inspector. I have also found a lot of really good information here on stackoverflow. The problem I cannot resolve is that cropping an image in code uses pixels but the rect I have is in points. Help!
This is what I am trying to do: I have an image that is full size on the iPhone. I want to capture a portion of the center of the image. But I want that portion to be the size of my rectangle.
In Xcode, I created a view with a uiimageview with the uiimageview view mode = center and Clip Subviews checked. Then, in code I set the image. Voila! My image is cropped at the center and displayed in the rectangular shaped view.
Can someone please help me do this in code? I've been trying different approaches for days....feeling pretty dumb by now.
Thank you in advance for your help.
I am creating an app for practice that is a simple drawing app. The user drags his/her finger along the screen and it colors in a 100px x 100px square.
I currently achieve this by creating a new colored UIView where the user taps, and that is working. But, after a little time coloring in, there is substantial lag, which I believe is down to there being too many UIViews as a subview of the main view.
How can I, and others who similarly create UIViews on dragging a finger reduce the lag to none at all, no matter how many UIViews there are. I also think that perhaps this is an impossible task, so how else can someone like me color a cube of the size stated above in the main view on a finger dragged along the screen?
I know that this may seem like a specific question, but I believe that it could help others understand how to reduce lag if there are a very large amount of UIViews where a less performance reducing option is available.
One approach is to draw each square into an image and display that image, rather than keeping around an UIView for each square.
If your drawing is simple enough, though, you can use OpenGL to do this, which is much faster. You should look at Apple's GL Paint Sample Code which shows how to do this in OpenGL.
If your drawing is too complex for OpenGL, you could create, for example, a CGBitmapContext, and draw each square into that context when the user drags their finger. Whenever you draw a new square into that bitmap, you can turn the bitmap into an image (via CGBitmapConxtextCreateImage) and display that image an a UIImageView.
There are two things that come to my mind:
1- Use Instruments tool to check if you are leaking any memory
2- If you are just coloring the views than instead of creating images for each of them, either set the background color property of UIView or override the drawRect method to do custom drawing
I think what you are looking for is the drawRect: method of UIView. You could create your custom UIView (you propably have that already) and override the drawRect method and do your drawing there! You will have to save your drawings in an array or another container and call the setNeedsDisplay method whenever the array content is changed.
I have two different UIImageViews. I'd like to make the top UIImageView blend in using the Screen blend mode with the bottom UIImageView.
I know of the property of CALayer: compositingFilter and I know that it doesn't work in iOS. I've searched a lot for solutions, and I've found how one should subclass UIView and override drawRect.
I've tried to set the context in drawRect to the screen blend mode, although it still draws every one of the images normally. Perhaps I am doing something wrong, or the approach should be different. Maybe I need OpenGL or CALayer to achieve this. Could someone assist?
Unfortunately there is no way to do a non-composite blend between UIViews on iOS. UIKit doesn't provide the functionality, and you've already noted, CALayer can't do it either.
In general, implementing -drawRect in a UIView won't help you. You're drawing into an empty bitmap -- it doesn't contain the bits of the views behind it, since those might change at any time (any view or layer might be animated). CA fundamentally assumes that layers' contents should be independent of each other.
You could try, in your -drawRect:
create an image context
capture the views under your view using -[CALayer renderInContext:] for each
create an image from the image context
draw that image into your view
set the blend mode and draw on top of that
But that will be slow and fragile, and won't work if you animate any of the views. I wouldn't recommend it.
If you really need to do this, you're going to have to switch your whole scene to render with OpenGL, where you've got more freedom.
Attached 1 is a screenshot from an app called GeniusScan where you can photograph any document and an adjustable rectangular grid shows on the imageview. You can easily adjust the borders of the grid with your fingers to select the portion of the image that you want to scan. It will be then transformed into the correct prospective.
1- How can I draw and interact with the grid on the imageview?
2- How can I return the corner points of the grid to my view controller.
Update: I found a wonderful class called BJImageCropper which allows to use fingers to ajust the borders, but only for a box like rectangle. Can anyone suggest how it can be updated to support shapes like in the GeniusScan app?
Dude:
I created a demo that solves both questions:
1- How can I draw and interact with the grid on the imageview?
By Adding 4 views that will act as interactive control points by adding UIPanGestureRecognizer and then drawing the grid using CAShapeLayer on top of your view.
2- How can I return the corner points of the grid to my view controller.
You must keep references to the four control points of your grid.
Here's the link to my code.
This isn't actually drawing on top of UIImageView. It's actually an overlay (view) on top of the UIImageView. You need to keep track of 4 points (have 4 views as subview of the layer), track their positions, once moved, use drawRect: to draw lines based on the 4 points.
The way I've implemented it in my app is, I overlay the UIImageView with a transparent 'SelectionView' (a custom view that I wrote). The selectionView contains 4 custom subview of class 'Vertex'. The vertex talk back to the selectionView via protocol method every time user touches/moves it (it's actually not important which vertex moved, just that it moved):
- (void)vertexMoved:(Vertex *)vertex;
Then the selectionView knows that it needs to re-draw, so it calls setNeedsDisplay which calls internally calls drawRect (you should never call drawRect) where I do the actual drawing of the bounding rect. Basically, iterate through each vertex and draw a line using Quartz APIs and fill it with semi transparent/hollow color.
This is how I am doing it atleast, I am sure there are other ways.
I want to place a series of images in a UIView... I want to be able to change each image's color using three different .png files (red,yellow,green) as a status indicator. Other than actually drawing the rectangle and filling it, is there an easier way?
Research effort: I have Googled and looked through SO and found nothing dealing with this.
There are lots of ways you can do this. I think the easiest way would be to pragmatically add UIViews as subviews to your main view, or to your parent UIView.
You can set the frame of your views as well as the background color. See this link
adding uiview as a subview to the main view
You can also use images, but since it is a plain solid color, its a lot of extra storage space, etc. to use images when you can programatically render a color.
If it is a series of rectangles, you can store UIViews in some kind of data structure so it is easier to dynamically change the color at runtime. If you aren't moving them around, then init there frames/geometry so they are in the correct location, then access them as members of an array or something similar.
If you want to add gradients to images, this is the best thing I have found:
Gradients on UIView and UILabels On iPhone
I figured it out... I took a UIButton, changed the Type to "Custom", sized it (32 x 32) and programmatically changed the the image depending on circumstances.
[button setImage:<#(UIImage *)#> forState:<#(UIControlState)#>]
Thanks to both of you for getting the thought process running... :D