I'm attempting to draw a path, and then mask it with another path using the DST_IN Porterduff Mode.
Here's my block of code that does the drawing
int saveCount = canvas.saveLayer(
0, 0, canvas.getWidth(), canvas.getHeight(), null);
canvas.drawPath(mPath, mFillPaint);
mClipPaint = new Paint();
mClipPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
canvas.drawPath(mClipPath, mClipPaint);
This does the masking but also has a rectangle around the path beyond which the masking doesn't work as seen below. The outer star is the original path and the blob is the masking path. You can see that the blob has a rectangular border beyond which masking doesn't work
As a side note, this only seems to work if hardware acceleration is enabled. Is this expected?
Related
Is it possible to realize the following picture in Android with canvas?
I want to have a hole and not only a Circle over the red layer which is yellow colored. I tried this (and failed) with the following Code in my onDraw()-Method:
canvas.drawBitmap(yellow, 0, 0, paint);
canvas.drawBitmap(red, 0, 200, paint);
Paint p = new Paint();
p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawCircle(300, 300, radius, p);
But when I use this code, it makes a hole through both bitmap's. At the end, this App should be a Maze with a ball, holes and other stuff. When the ball would fall into a hole it should appear under the red-Bitmap. Is it possible to realize this?
Answer:
If someone should have the same problem: use View and not SurfaceView. That was my fault, because the bg of a SurfaceView could not be set transparent.
I think you're misunderstanding how the canvas/bitmaps work. There aren't layers or objects stored (unless you store them). It's just a pixel by pixel representation of the image displayed. A yellow circle over a red square is what you have shown in the above picture.
If you truly want a red layer, you have to composite two bitmaps. Draw the hole over the red square in one bitmap, draw the yellow layer in one bitmap. On the canvas, draw the yellow bitmap, then the "red square with a hole" bitmap on top.
I have a bitmap that spans the whole screen that will function as texture for a Path object that I need to draw to my canvas. I then have a background image that this textured path needs to be drawn on top of.
I tried using the PorterDuff modes, but nothing seemed to work correctly. I was having a hard time figuring out exactly how the PorterDuff modes act, because none of them seem to act the way I always thought they were supposed to function.
I've figured out a way to texture the path with this test code:
Paint paint = new Paint();
//draw the texture
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.texture),0,0,paint);
//construct the Path with an inverse even-odd fill
Path p = new Path();
p.setFillType(Path.FillType.INVERSE_EVEN_ODD);
p.addCircle(this.getHeight()/2, this.getWidth()/2, 200, Path.Direction.CCW);
//use CLEAR to remove inverted fill, thus showing only the originally filled section
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.CLEAR));
//draw path
canvas.drawPath(p, paint);
But I can't figure out how to then place that on top of a background image. Am I just using the PorterDuff modes wrong?
Maybe my questions could lead you to your solution:
The paint used in your drawPath call:
What is the paint style?
What is the paint stroke width?
What is the paint stroke/fill color?
If you are not using a stoke/fill color, but a texture instead, where is the call to the paint's setShader (using a BitmapShader)?
The only part of my app that is still software rendered is the rendering of one view where I need to draw a round bitmap. I'm using clipPath to clip the bitmap that I need to render to the round shape.
I understand that clipPath is not hardware accelerated, but I am looking for an algorithm that would allow me to provide the equivalent functionality using hardware acceleration.
Specifically I need to create a round clipping region of a source bitmap and have that rendered to my canvas.
If you have to use clipPath you could shut down the hardware acceleration as below.
<application
android:label="#string/application_name"
android:hardwareAccelerated="false">
And you also could control hardware acceleration among Application, Activity, Window and View layers. Detail information describes on this Hardware Acceleration article on Android Development web site.
You could try to this, though I am not sure it is hardware accelerated :
in onCreate :
create a paint (called bitmapPaint) that uses setXfermode :
http://developer.android.com/reference/android/graphics/Paint.html#setXfermode(android.graphics.Xfermode)
put an AvoidXfermode, also its deprecated, it work pretty well. Pass it the white color and target mode with a high tolerance (like 240)
in onLayout :
create a bitmap of the same size as your view
draw your circle inside on of its canvas, in white, using anti alias for a clean border
in onDraw :
draw the bitmap with the white circle in your paint canvas
now, draw your bitmap inside your paint canvas using the bitmapPaint you created in onCreate
The bitmap should be rendered inside the circle only.
If your bitmap does not change a lot, clip it once to the shape into a new bitmap, and then draw the clipped bitmap in your onDraw.
Here is an example how to clip a circle from a source bitmap
Bitmap bitmap = Bitmap.createBitmap(source.getWidth(), source.getHeight(), Bitmap.Config.ARGB_8888);
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
Canvas canvas = new Canvas(bitmap);
paint.setColor(Color.RED);
// Draw your shape here
canvas.drawCircle(cx, cy, radius, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(sourceBitmap, 0, 0, paint);
So this is what I have for a vignette style effect in Android (image is a Bitmap):
public void vignette() {
float radius = (float) (image.getWidth()/1.5);
RadialGradient gradient = new RadialGradient(image.getWidth()/2, image.getHeight()/2, radius, Color.TRANSPARENT, Color.BLACK, Shader.TileMode.CLAMP);
Canvas canvas = new Canvas(image);
canvas.drawARGB(1, 0, 0, 0);
final Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
paint.setShader(gradient);
final Rect rect = new Rect(0, 0, image.getWidth(), image.getHeight());
final RectF rectf = new RectF(rect);
canvas.drawRect(rectf, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(image, rect, rect, paint);
}
This "works" but there are a couple of problems. First of all, this is not really a vignette, it's just a gradient so you can see bits of the black going nearly all the way to the center rather than feathering out closer to the edges.
The RadialGradient used also only allows for setting the radius of a circle rather than an ellipse. An ellipse would be able to more effectively match the dimensions of a non-square image than a circle.
The quality of the gradient is also not superb.
I'm trying to replicate the vignetteImage method from ImageMagick (I'm referring specifically to the php version). I have this code in PHP that produces the style of image that I want:
$im = new IMagick('city.png');
$im->vignetteImage($width/1.5, 350, 20, 20);
I've tried building ImageMagick with the NDK but have been unsuccessful in properly linking the various image libraries (I've only successfully built with gif support but no png, jpeg or tiff).
I've also attached an image comparing the two methods shown above. The image on the left was generated with ImageMagick through php and the image on the right was generated using the method shown above for Android.
If you look carefully at the image on left, tf uses exponential increase in Alpha (transparency) vs. image on right which is very linear.
Clearly Shader.TitleMode.CLAMP is a linear function. What you should do instead is use RadialGradient(float x, float y, float radius, int[] colors, float[] positions, Shader.TileMode tile) to define 10 or more points on the image with exponentially decreasing color values (black to transparent).
Alternatively, you can refer gallery 3d source for ICS gallery http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android-apps/4.0.1_r1/com/android/gallery3d/photoeditor/filters/VignetteFilter.java?av=h
I know this is an old discussion but it may help someone.
You can use AccelerateInterpolator to generate the points that Taranfx had mentioned and it will lock awesome.
I'm developing an android app where i need to capture text and save it as a transparent image. Capturing the text has been done but making a transparent png file is where i'm stuck as i'm not familiar with image pixel manipulation at all. Here's what I have so far... i first create a blank bitmap and fill it with a white background, then i set the paint's transparency to 0 (full transparency) and then draw the source bitmap into the destination bitmap using the XOR modes.. but when i run the app all i see is a blank white image. i'll be glad if someone points out what i'm doing wrong and how to fix it. Thanks in advance.
b = Bitmap.createBitmap(tw, th,Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(b);
Rect dest = new Rect(0,0,b.getWidth(),b.getHeight());
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.WHITE);
canvas.drawRect(0, 0, b.getWidth(), b.getHeight(), paint);
paint.setAlpha(0);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.XOR));
canvas.drawBitmap(bmp,null,dest,paint);
Have you looked at : How to change a bitmap's opacity?
Seems like
paint.setAlpha(0);
won't do anything as you need to set the alpha channel to something greater than 0...
Use:
Color.argb(0,0,0,0)
The first parameter is the alpha. Set it to 0 for complete transparency.