Android :: Draw Transparent Lines On Bitmap Via Touch Input
Jul 23, 2010
I am working on a paint application for Android. Now I want to implement an eraser to allow erasing parts of a loaded bitmap by using touch input and making the bitmap transparent along the finger's path.
A very good example of what I try to achieve is shown in the application Steamy Window for Android. Steamy Window simulates a fogged window, where a user can wipe parts of the fog via touch input.
UPDATE: I have posted the most important sections of my current code below. I am not really happy with it for the following reasons:
Drawing is quite sluggish. What can I improve here?
I am looking for a way to use an alpha mask in order to set the pixel transparency/alpha of the pixels as I want to simulate a paint brush. Any suggestions how this could be achieved?
CODE:...................
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Feb 9, 2010
To draw a scalable rectangle around a bitmap
And such that
1) The rectangle should scale based on the size of my bitmap
2) The colour of my rectangle should change on my input
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Apr 2, 2009
I am 1) taking a picture and 2) then draw another Bitmap on top of it 3) then I store it
I am doing it as follows and it works on the emulator.
On the device I get a OutOfMemoryError: bitmap size exceeds VM budget android.graphics.Bitmap.nativeCopy(Native Method) android.graphics.Bitmap.copy(Bitmap.java:199) in the line copy the Bitmap to get a mutable Bitmap.
CODE:...........
What I am asking:
a) Is there a better way to do what I am doing? 1) take a picture 2) draw another Bitmap on top of it 3) then I store it
b) What is the best way to create a mutable Bitmap from the picture I just took with the camera?
In my app, resolution is not an issue. If it works better for small photos that would be fine.
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Oct 8, 2009
I have two questions actually:
Is it better to draw an image on a bitmap or create a bitmap as resource and then draw it over a bitmap? Performance wise... which one is better?
If I want to draw something transparent over a bitmap, how would I go about doing it?
If I want to overlay one transparent bitmap over another, how would I do it?
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Mar 22, 2009
My goal is the draw a bitmap onto another bitmap but rotated 90 degress. whats the most efficient way to do that. My current method is as follows which is horribly bad because it creates a new bitmap every time.
CODE:.....................
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Apr 28, 2010
How to draw different types of lines like thick line, dashed line etc using opengl android?
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Aug 26, 2010
I am drawing several lines on a canvas using drawline, the lines are semi transparent (their paint has an alpha value <255) only problem is that the point at which they cross creates a dot of less transparent color (obviously) is there a simple way to avoid this?
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May 7, 2010
i have a customized LinkedEditText extends from EditText, and override the onDraw method as below:...........................
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Dec 29, 2009
what is best way to create app in which I only need to draw simple lines through onTouchEvent? When i use invalidate everytime i draw any line, that erase lines i draw before. But if I use some List structure to store drawed lines it lose performance. Is there any simple way to do it?
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Aug 14, 2010
What is the simplest way to draw pixels, lines and circles on a View?I want to move a cross cursor around, so nothing particularly intensive.I thought I could extend SurfaceView and add it to an XML and it would just work, but it just appears black, however, when I look at the layout view of localmap.xml in eclipse, the graphics appear as expected. Any ideas? My onDraw is never called on the emulator, and even calling invalidate on the class makes no difference. I shall keep trying but can anyone see anything I've missed? or is there a better way entirely? Code...
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Nov 11, 2010
I'm writing an app that shows in google maps pipes and valves(lines and points). For that i've two classes.
One extends from ItemizedOverlay, and i add to map overlay one for each category of valve, and each one can have more than one item.
The second extends from Overlay, and in the draw method y draw the line with the method drawline of the canvas.
The problem i've is that the lines are drawn over the ItemizedOverlay items, no matter the order i add them to the mapView.getOverlays().
I want the lines on the bottom of all overlays. is there a way to do that.
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Jun 22, 2010
I want to draw a shape(many circles particularly) into a Specific Bitmap. I have never used canvas / 2D graphs etc. As i see it i create a Drawable put the bitmap in it then "canvas-it" to the shapes i want etc.
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Nov 20, 2010
I tried enough to find in google & android this question. Also did several trials & errors, but couldn't get this question. was learning Android's "Draw Nine Patch" images. One basic I know is that, whatever image you process must be in .png format (if it's already in .9.png then it will be ignored by tool). However, couldn't understand what it literally means by "stretchable patches" ? what exactly happens when you draw black dots outside the .png image ? (preview pane shows changes happening, but I am unclear on how it makes those)When I draw black dots in left/top sides of image it shows some changes in preview; but why isn't there any effect when you do the same on right/bottom side of the image ? why this tool is used primarily for background, when we try to process on the image itself ?i am trying to modify a simple button.png (given in android sdk). Whenever I use this tool & draw black lines, it reduces the size of the image instead of 'stretching' it! Why ?What is the significance of options given below like, "show lock", "show content", "Patch scale" and so on ?I apologize for asking so many questions, but in Android online docs they haven't explained well for novice. If someone can answer these, it will become ready reference for all the begineers who search this forum.
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May 25, 2010
I have a calculator type app that I've developed and it's on the Android Market. It uses two input-lines (EditText) and has always worked well until I updated my Nexus One to Android 2.2.
When I would touch the input line, the soft keypad would pop-up automatically, lift up the focused input line into view, and then I would type in my numbers...no problems. But when I updated to Android 2.2, the soft keypad doesn't lift the focused input line far enough and it's only half in view. Then when I scroll down to the next input line, it doesn't lift up either and it's only about 1/4 of the way into view. Another problem is that, sometimes, when I go back and forth between the two input lines and then try to enter numbers - the numbers don't appear but they do when I scroll left. Hard to explain exactly what is happening but something strange is going on there that didn't happen under my Android 2.1 and other lower versions.
I even tried to change some input line (EditText) statements in my code and also tried to change the way the soft keypad would 'pad' the view to the top but things still didn't work after I recompiled. (android:windowSoftInputMode and android:inputType)
I also wonder if they made the soft keypad in 2.2 a little bigger in height. Does anybody out there with 2.2 mess with an app that has input lines where their softkeypad has to move the input line up into view - does it work for you?
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Aug 15, 2010
Hopefully this is a simple one as I've been asking loads recently...
I am trying to draw the a white circle with the following code...
but it is being displayed as a solid disk, how do I get it to just display as an circular outline with a transparent centre?
I've had a look in the help and it makes no sense to me, probably because I'm not used to the drawing terms like stroke and dither. What's wrong with background and border eh?
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Jan 8, 2013
I am wondering if there is a way to draw an image, or edit simple lines in a text box. The entire screen is a textView/ect and i would like to be able to write a sentence then draw an image and write again. By draw i think i would use the Canvas, so basically is there a way to include a canvas in a text view?
Evernote does do this, but to edit an image/draw you need to open another app "Skitch", my goal is to try and do this without any extra apps.
For example:
Hello
(canvas/editable graphical items)
World
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Jul 6, 2010
My objective is to run a glowing animation on an image.I am changing the image alpha to produce this effect.
I have used basic AlphaAnimation provided in android framework but found that its slowing down other animations. So i extended a class from SurfaceView and created a thread to update it. ( Again here, i am manipulating alpha of the image ).
Everything seems fine, except that i am not able to draw a transparent image onto SurfaceView.Its showing black color on the transparent areas of the bitmap.code...
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Aug 10, 2010
I'm passing a bitmap through a bundle to an activity which I called cameraView on which the user has access to the camera of the device. I'd like to overlay that bitmap with transparency using the camera as the background. Is it possible? to put the bitmap in front of the camera? And how can I change the transparency level? Here is my code: This is the camview.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:orientation="vertical">
<SurfaceView android:id="@+id/surface_camera" android:layout_width="fill_parent"
android:layout_height="10dip" android:layout_weight="1"> </SurfaceView> </RelativeLayout>
And this is the java:
public class cameraView extends Activity implements SurfaceHolder.Callback{
SurfaceView mSurfaceView; SurfaceHolder mSurfaceHolder;
Camera mCamera; boolean mPreviewRunning=false; private Context mContext = this;
public void onCreate(Bundle icicle) { super.onCreate(icicle);
setContentView(R.layout.camview); Bundle f = getIntent().getExtras();
picture = f.getParcelable("bitmap"); mSurfaceView = (SurfaceView) findViewById(R.id.surface_camera); mSurfaceHolder = mSurfaceView.getHolder();
mSurfaceHolder.addCallback(this); mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
} @Override // Create the Surface and Open the Camera
public void surfaceCreated(SurfaceHolder holder) { mCamera = Camera.open();
} @Override // Reacts for camera changes public void surfaceChanged(SurfaceHolder holder,
int format, int w,int h) { if (mPreviewRunning) { mCamera.stopPreview();
} Camera.Parameters p = mCamera.getParameters(); p.setPreviewSize(w, h);
mCamera.setParameters(p); try { mCamera.setPreviewDisplay(holder);
} catch (IOException e) { e.printStackTrace();
} mCamera.startPreview(); mPreviewRunning = true;
} @Override // When the camera is closed
public void surfaceDestroyed(SurfaceHolder holder) { mCamera.stopPreview();
mPreviewRunning = false; mCamera.release(); }
// When the picure is taken. This method gives the byte[] of the picture
Camera.PictureCallback mPictureCallback = new Camera.PictureCallback() {
public void onPictureTaken(byte[] imageData, Camera c) {
} };
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Nov 11, 2010
I'm trying to figure out how to draw on a bitmap in android, and keep a copy of these changed bitmaps for an undo function.
Bitmap b = ...
Paint p = new Paint();
canvas.drawBitmap(b, new Matrix(), null);
canvas.drawCircle(0,0,20,20);
//does Bitmap b have the circle drawn on it next time?
Or how do I get the bitmap after its been drawn on with the canvas(I want to preserve a stack of bitmaps with the changes applied by canvas drawing)? Maybe I'm going about this entirely wrong.
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Oct 8, 2010
I have an android application to display an image on another. the second image's white color should be converted in to transparent. so i used two imageviews. the original image to be overlayed is bitmap1. image after making transparent is bitmap2. when i run this i got some exceptions atsetPixel method. the code ...
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Jun 14, 2009
Can i draw text on a bitmap? I cannot find any API support this.
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Nov 4, 2009
I have an application that uses GLSurfaceView to draw OpenGL ES graphics. This is all working (mostly) how I would expect.
Now, I would like to implement a screenshot feature. For normal views, it seems that the standard practice is to create a new Canvas with a Bitmap and then draw to that Canvas using View.onDraw(Canvas).
I've tried using SurfaceView.draw(Canvas) in a similar fashion, but it always results in a blank (black) image.
I've also tried using the drawing cache with the exact same result.
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Dec 2, 2009
Any one know about how to draw a bitmap image?...
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Nov 12, 2009
I've been trying almost everything and been searching and reading everywhere on the net. I just can't seem to find the correct way of doing this.
I have a MapActivity with a MapView and I want to draw something on an Overlay. I'm overwriting the draw-method, and I can easily draw straight on the canvas using a paint. My problem is I want to merge some circles and afterwards color them. Therefore I want to create a Bitmap and then draw on that. I just don't know what to use. Should I use a mutable Bitmap, a BitmapDrawable or am I simply going in the wrong direction.
The reason I want to do this is because I want to draw some kind of heatmap upon the Google Maps, and I need to merge and blend different circles, so they appear to be just one big blob.
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Mar 9, 2009
I'm creating a simple game for Android and faced with a problem: Idea is to have a huge "map" image file and re-draw only small part of it (320*480) depending on user actions.
I didn't find a better solution than using "public static Bitmap createBitmap (Bitmap source, int x, int y, int width, int height)" method and decided to try it (expected huge performance degradation), but actually it's appeared that this method changes source bitmap and when i call it second time source size is significantly reduced. For instance this code:
CODE:.................
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Aug 30, 2010
I have a byte array of RGB values, just like the contents(without header) of a *.bmp file. What I want to do is, draw the corresponding bitmap on Android, using OpenGL.
It seems that OpenGL ES doesn't have a single API that will do, it true?
If true, how can I do this?
Actually, I can draw it in JAVA code, but it's too slow and costs too much CPU time. So I want to try drawing it with OpenGL. Is there any other advises? Or maybe OpenGL can't be the right answer?
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Dec 25, 2009
What 's the fastest way to display a bitmap? Now I am using Bitmap.setPixels and ImageView.setImageBitmap all time that this change. It has a refresh of 15 fps. It work good, but I am not sure that is the best method to get best performance. Is better use Canvas.drawBitmap with a SurfaceView ? or opengl ?
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Mar 26, 2009
In my Java code I am setting the content of an ImageView to a Bitmap. However, before doing so I want to clip the Bitmap to a circular region. How would I go about this? I've been looking for some API that would let me set the alpha channel of the Bitmap to fully transparent for all pixels outside the circular region.
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Mar 1, 2010
I want to draw a bitmap on the screen by specifying the x,y locations of the four corners. I.e. I have a square bitmap and I would like to draw the:
CODE:.........
I have seen the Canvas method: public void drawBitmap (Bitmap bitmap, Rect src, RectF dst, Paint paint)
However I believe this takes the top, right, bottom and left coordinates to draw the Bitmap and not the corner coordinates. I need to specify the CORNER coordinates to draw the bitmap as I may need to stretch/distort the Bitmap (I am drawing the Bitmap on a 3D spherical model).
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Aug 6, 2009
I created a layout xml file that contains an extended textview. What I want is to draw the textview in a bitmap. What do I have to do after inflating the view so that I can use the draw method on the my canvas?
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