Android :: Convert A Bitmap To GrayScale In Droid?
Jul 30, 2010
I am new to this site, and I come with a question about Android.
Is there any way to convert a Bitmap to grayscale? I know how to draw a grayscale bitmap (using canvas operations: http://www.mail-archive.com/android-developers@googlegroups.com/msg38890.html) but I really need The actual bitmap in gray colors (or at least something that could be converted to a bitmap later on).
Do I have to implement it by hand (pixel by pixel operations)?
I've searched a lot, and still could not find. Anyone knows a easy/efficient way to do it?
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Oct 28, 2010
I am trying to use one of these algorithms to convert a RGB image to grayscale :
The lightness method averages the most prominent and least prominent colors:
(max(R, G, B) + min(R, G, B)) / 2.
The average method simply averages the values: (R + G + B) / 3.
The formula for luminosity is 0.21 R + 0.71 G + 0.07 B.
But i get very weird results ! I know there are other ways to achieve this but is it possible to do this way ?
here is the code...
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Apr 20, 2009
I am trying to grayscale bitmap as follows, But it is crashing as soon as I run this method.
The problem is in last line. How can I assign "int" to "Color"? Or are there any better ways?
CODE:................
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May 20, 2009
I would like to convert a Bitmap to a grayscale array of bytes (one byte per pixel). At the same time I want to just crop at section from the middle. Having looked though the various api's it is not clear to me what the best way would be.
1) What is ALPHA_8? is that grayscale? I have a feeling that the grayscale effect should be done via some "saturation" on the paint object, right?
2) once I have the Bitmap in grayscale and the right size, what is the best way to get that to a byte[] of pixels (one byte per pixel)?
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Jul 8, 2009
I have a camera application that captures a 640x480 image.I want to convert this image to grayscale.I know I have to use the setSaturatio (float sat) in the ColorMatrix method to zero but I don't know how I can set it to grayscale.
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Mar 10, 2010
How can i convert a Bitmap image to Drawable.
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Mar 10, 2010
How can i convert a Bitmap to Drawable.
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May 10, 2010
I will try to explain what exactly I need to do.
I have 3 separate screens say A,B,C. There is another screen called say HomeScreen where all the 3 screens bitmap should be displayed in Gallery view and the user can select in which view does he wants to go.
I have been able to get the Bitmaps of all the 3 screens and display it in Gallery view by placing all the code in HomeScreen Activity only. Now, this has complicated the code a lot and I will like to simplify it.
So, can I call another Activity from HomeScreen and do not display it and just get the Bitmap of that screen. For example, say I just call HomeScreen and it calls Activity A,B,C and none of the Activities from A,B,C are displayed. It just gives the Bitmap of that screen by getDrawingCache(). And then we can display those bitmaps in Gallery view in HomeScreen.
I hope I have explained the problem very clearly.
Please let me know if this is actually possible.
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Feb 28, 2010
How do I convert a Drawable into a Bitmap?
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Jun 4, 2009
I am trying to figure out how to do conversion of Picture object generated by web View to Bitmap for later JPEG encoding and saving to local f/s. I tried to create a bitmap from pre created Picture object by BitmapFactory.decode Stream and failed. Seems like Picture object is unrecognized format by Bitmap factory. Just wondering is there any method to do the conversion?
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Sep 2, 2010
I'm trying to convert my LinearLayout to a bitmap so that I can save the current layout content as an image in SD card. First, I create bitmap and canvas and attach the layout to the canvas.
Followed steps from http://www.brighthub.com/mobile/google-android/articles/30676.aspx#comments.
Code to add child view into layout before creating bitmap:
CODE:............
When I press the save button, it should save the current layout as an image to SD card.
Here are my steps:
CODE:...............
It can create folder in SD card but no file created under this folder. It always gives me FileNotFoundException. I'm not sure it is the file creating problem or the screenBitmap problem.
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Mar 19, 2009
I want to store image in sqlite database. I tried to store it using BLOB and String, in both cases it store the image and can retrieve it but when i convert it to Bitmap using BitmapFactory.decodeByteArray(...) it return null. Below is my code please have a look and suggest me where i m making mistake.
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Aug 12, 2010
Does anyone know how to convert a bitmap to a byte array?
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May 29, 2009
I want to store pictures from the internet in my data base as byte arrays. I get the pictures as bitmaps, but can't find way to convert it to byte array.
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Sep 27, 2010
I have a problem in converting base64 string to bitmap in android. I am using the camera to fetch the image and i am convert the image to base64 string to post to the server. I want to show that image in the imageview so how can i show the image in the ImageView after fetching the image from the camera.
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Nov 3, 2010
For some reason, when I create a bitmap from an image in asset, it does not display fullscreen. When I take an image from drawable, resId, the image shows fullscreen. Why is this?
CODE:..........................
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Jan 25, 2009
How do I get a bitmap of a webview? I think I can use the capturePicture but how do I then convert that picture object to a bitmap that I can clip and manipulate?
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Jul 5, 2010
I've seen this code on the web...
My questions are:
1. Is 'bmp' supposed to be the color bitmap I want to affect?
2. How do I get the 0-255 value of the grayscale?
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Jul 21, 2010
I have a very large image and I only want to display a section the size of the display (no scaling), and the section should just be the center of the image. Because the image is very large I cannot read the entire image into memory and then crop it. This is what I have so far but it will give OutOfMemory for large images. Also I don't think inSampleSize applies because I want to crop the image, not lower the resolution.
Uri data = getIntent().getData();
Input Stream is = getContentResolver().openInputStream(data);
Bitmap bitmap = BitmapFactory.decodeStream(is, null, null);
Any help would be great?
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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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Nov 24, 2009
What would be the right way to turn a color Drawable into a grayscale one (to indicate disabled state)?
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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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Oct 7, 2012
I am wondering how do I go about writing code (or be directed to any existing relevant code), that allows me to average the grayscale values above a threshold (Otsu threshold) from a JPEG photo taken from an android device camera.
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May 8, 2013
What I am needing is a method to get grayscale pixel data from an image or preview. I am not interested in saving the picture as a jpeg etc, just need the grayscale data.
I am aiming at API 10 (as this is the device available for testing).
On top of this, I am not having any luck getting the camera to work on the Eclipse emulator.
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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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May 15, 2010
Basically I want to capture webpage from webview and get raster data of the bitmap. code...
Issue 1: Out of memmory exception when web page is big for eg. http://times.com What should I do to get this image? Is it possible to get image in multiple bitmaps?
Issue 2: How can i get RGB data 24 bit data from ARGB_8888. I need to get this 24 bit Raster data compress it with some compression and process it...
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Feb 17, 2010
I have developed the application in android and i installed the application in to HTC magic mobile , it's working good. but i want to install same application in Droid mobile(480x854 px) , shall i need to modify any code for that?
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Jul 24, 2010
Has anyone tried to convert an android app to iPhone iOS? Is that even possible?
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Jul 1, 2010
I am using a html parser called jsoap, to load and parse html files. The problem is that the webpage I'm scraping is encoded in ISO-8859-1 charset while Android is using UTF-8 encoding(?). This is results in some characters shows up as question marks. So now I guess I should convert the string to UTF-8 format. Now I have found this Class called CharsetEncoder in the Android SDK, which I guess could help me. But I can't figure out how to implement it in practice, so I wonder if could get som help with by a practical example.
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