Hello friends!
I need to create a photo editor, which allow to put the emoticons, text and drawing with a brush on the picture.
Open the illustration
An editor must be able to change the position of smiles & text, their size and rotation with two fingers (multi-touch).
Mechanics is clear to me. I found ready realization of multi-controller:
https://github.com/lukehutch/android-multitouch-controller
But I don't understand how better visualize all the layers in terms of performance:
Layer 3 - text
Layer 2 - emoticons
Layer 1 - drawing
Layer 0 - photo
I am afraid to use the canvas, without your opinion. I heard that the canvas buggy when displaying a large number of images.
I found examples visualize the layers of images using layer-list with the 's inside. I think this method will be more performance numbers for my task.
But I have not found documentation of how to update the position (top / left) when you move an item.
My question is: What is the best use for the visualization of all layers and the possibility to save the final image (merge all layers)?
Please help, what to choose and what is the right path!
Thank you in advance! :)
Canvas is not buggy. It's the only way for you to render things onto a Bitmap. By the looks of your requirement, I think you need to draw your Layers onto different bitmaps. Layer 0 will be your default bitmap. Every other layer will be individual bitmaps on their own. The reason they have to be on a bitmap of their own is so that you can move them as you wish.
You final merge will be to draw all these bitmaps, on the default bitmap via Canvas.drawBitmap() call.
Im looking for Android 2D framework which allows me to create canvas layer on which I can draw simple shapes like rect, oval atc (raster graphics). The canvas have to PERSIST everything I draw on it.
I found many engines (libgdx, andengine ...) but if they have capability to draw shapes, its only for one screen update. Reason becouse I dont store drawn shapes to some kind of List is becouse in app, the drawing occurs every screen update so I just want to modify canvas and dont remember anything.
Thanks for every answer.
As far as I know, android doesn't support something like that. Android uses double-buffering which means 2 alternatives "screens" that alternate each other so if you draw on one the next would be on random state.
There are tricks you can use to achieve what you want like draw both screens and then stop drawing, but android doesn't support such behavior because when you get hold of a canvas it's not certain that it returned exactly as what you did last frame, it doesn't specify what could cause an error, but if you ask me it could be anything that pops up on screen.
You don't really need an engine to do that, you can use a SurfaceView and draw on it (it supports shapes like the ones you want)
I noticed on MIT app inventor that there is no way to clear a canvas without using the .clear method. This means that you would have to manually redraw the whole screen every time you update it, right? So, what do you do in order to avoid blinking when you redraw your objects. Is there a way to have a whole canvas behind the first in order to avoid blinking, and then update it, or do you just have to deal with the blinking how it is.
I realize that it is quite possible to make an array/list of every pixel on the screen, with an int for the RGB value of each pixel, and then just draw to that list. Then you can simply copy the array to the screen to render. I think this would be excessively slow and tedious in a language as simple as MIT app inventor.
what you could do is to store your canvas as image and later assign that image to the canvas background again... see also How to Save a Canvas
You also might be interested in Scott's Paintpot mod undo and redo example here
I realize that it is quite possible to make an array/list of every pixel on the screen, with an int for the RGB value of each pixel, and then just draw to that list.
exactly, this will be slow
btw, you can find more Canvas examples (and also other stuff) from Scott here
Let me give you some substance to my question. I am currently drawing 2 or more full screen drawables to my canvas. The drawables in the foreground slide at different speeds and have large transparent sections to create a shifting scene. (Think side scroller game like mario. I believe they call this parallax)
I then follow that up with several smaller drawables in the foreground that move and do their own thing.
At present drawing all these drawables to my canvas is very taxing on my device. Is there a way to use Bitmaps to programmatically and dynamically layer them while maintaining the alphas, to achieve the same affect and reduce the number of times I call drawBitmap on my canvas?
Thanks
I'm tried to determine the "best" way to scroll a background comprised of tiled Bitmaps on an Android SurfaceView. I've actually been successful in doing so, but wanted to determine if there is a more efficient technique, or if my technique might not work on all Android phones.
Basically, I create a new, mutable Bitmap to be slightly larger than the dimensions of my SurfaceView. Specifically, my Bitmap accomodates an extra line of tiles on the top, bottom, left, and right. I create a canvas around my new bitmap, and draw my bitmap tiles to it. Then, I can scroll up to a tile in any direction simply by drawing a "Surfaceview-sized" subset of my background Bitmap to the SurfaceHolder's canvas.
My questions are:
Is there a better bit blit technique than drawing a background bitmap to the canvas of my SurfaceHolder?
What is the best course of action when I scroll to the edge of my background bitmap, and wish to shift the map one tile length?
As I see it, my options are to:
a. Redraw all the tiles in my background individually, shifted a tile length in one direction. (This strikes me as being inefficient, as it would entail many small Bitmap draws).
b. Simply make the background bitmap so large that it will encompass the entire scrolling world. (This could require an extremely large bitmap, yet it would only need to be created once.)
c. Copy the background bitmap, draw it onto itself but shifted a tile length in the direction we are scrolling, and draw the newly revealed row or column of tiles with a few individual bitmap draws. (Here I am making the assumption that one large bitmap draw is more efficient than multiple small ones covering the same expanse.)
Thank you for reading all this, and I would be most grateful for any advice.
I originally used a similar technique to you in my 'Box Fox' platformer game and RTS, but found it caused quite noticeable delays if you scroll enough that the bitmap needs to be redrawn.
My current method these games is similar to your Option C. I draw my tiled map layers onto a grid of big bitmaps (about 7x7) taking up an area larger than the screen. When the user scrolls onto the edge of this grid, I shift all the bitmaps in the grid over (moving the end bitmaps to the front), change the offset of grid, and then just redraw the new edge.
I'm not quite sure which is faster with software rendering (your Option C or my current method). I think my method maybe faster if you ever change to OpenGL rendering as you wouldn't have to upload as much texture data to the graphics card as the user scrolls.
I wouldn't recommend Option A because, as you suggest, the hundreds small bitmap draws for a tiled map kills performance, and it gets pretty bad with larger screens. Option B may not even be possible with many devices, as it's quite easy to get a 'bitmap size exceeds VM budget' error as the heap space limit is set quite low on many phones.
Also if you don't need transparency on your map/background try to use RGB_565 bitmaps, as it's quite a lot faster to draw in software, and uses up less memory.
By the way, I get capped at 60fps on both my phone and 10" tablet in my RTS with the method above, rendered in software, and can scroll across the map smoothly. So you can definitely get some decent speed out of the android software renderer. I have a 2D OpenGL wrapper built for my game but haven't yet needed to switch to it.
My solution in a mapping app relies on a 2 level cache, first tile objects are created with a bitmap and a position, these are either stored on disk or in a Vector (synching is important for me, multithreaded HTTP comms all over the place).
When I need to draw the background I detect the visible area and get a list of all the tiles I need (this is heavily optimised as it gets called so often) then either pull the tiles from memory or load from disk. I get very reasonable performance even on slightly older phones and nice smooth scrolling with no hiccups.
As a caveat, I allow tiles not to be ready and swap them with a loading image, I don't know if this would work for you, but if you have all the tiles loaded in the APK you should be fine.
I think one efficent way to do this would be to use canvas.translate.
On the first drawing the entire canvas would have to be filled with tiles. New android phones can do this easily and quickly.
When the backround is scrolled I would use canvas.translate(scrollX, scrollY), then I would draw individualy one by one tile to fill the gaps, BUT, I would use
canvas.drawBitmap(tileImage[i], fromRect, toRect, null) which would only draw the parts of the tiles that are needed to be shown, by setting fromRect and toRect to correspond to scrollX and scrollY.
So all would be done by mathematics and no new bitmaps would be created for the background - save some memory.
EDIT:
However there is a problem using canvas.translate with surfaceView, because it is double buffered and canvas.translate will translate only one buffer but not the second one at the same time, so this alternating of buffers would have to be taken into account when depending on surfaceView to preserve the drawn image.
I am using your original method to draw a perspective scrolling background. I came up with this idea entirely by accident a few days ago while messing around with an easy technique to do a perspective scrolling star field simulation. The app can be found here: Aurora2D.apk
Just tilt your device or shake it to make the background scroll (excuse the 2 bouncing sprites - they are there to help me with an efficient method to display trails). Please let me know if you find a better way to do it, since I have coded several different methods over the years and this one seems to be superior. Simply mail me if you want to compare code.