Develop Reference

Android canvas positioning, and customization

So this is my scenario:
I have an svg image that contains all the music notes on the staff (sort of sprite sheet)
I have two svg image that contains the key (maybe i can merge them together anyway)
All of them are converted to android Vector Drawable.
What i want to do is to select the note from the first svg, select the cleff, and then show them next to each other (the two images should be aligned).
So what i managed to achieve is to select the portion of svg for the note (i need to refine the rect size). But what i'm still having problem is to show both of them on the same line.
public MusicScore(Context context) {
super(context);
paint = new Paint();
paint.setColor(Color.BLACK);
Resources res = context.getResources();
musicClef = (VectorDrawable) res.getDrawable(R.drawable.ic_bassclef, null);
musicNotes = (VectorDrawable) res.getDrawable(R.drawable.ic_musicnotes, null);
int width = getWidth();
int height = getHeight();
Log.i("MUSIC", "H: " + musicClef.getMinimumHeight() + " W: " + musicClef.getMinimumWidth());
}
#Override
protected void onDraw(Canvas canvas){
Log.i("MUSIC", "Called");
int left = getWidth()/2;
int top = getHeight()/2;
musicClef.setBounds(0,0,musicClef.getIntrinsicWidth(), musicClef.getIntrinsicHeight() );
Bitmap source = Bitmap.createBitmap(musicNotes.getIntrinsicWidth(), musicNotes.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
Bitmap clefSource = Bitmap.createBitmap(musicClef.getIntrinsicWidth(), musicClef.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
Canvas newcanvas = new Canvas(source);
Canvas clefCanvas = new Canvas(clefSource);
int notesLeft = musicClef.getIntrinsicWidth();
int notesTop = musicClef.getIntrinsicHeight();
musicNotes.setBounds(0, 0, musicNotes.getIntrinsicWidth(), musicNotes.getIntrinsicHeight());
musicNotes.draw(newcanvas);
musicClef.draw(clefCanvas);
Rect rect = new Rect(1150,0,1700, musicNotes.getIntrinsicHeight());
Rect rect2 = new Rect(notesLeft ,0, notesLeft + 450, musicNotes.getIntrinsicHeight());
Rect clefRect = new Rect(0, 0, musicClef.getIntrinsicWidth(), musicClef.getIntrinsicHeight());
canvas.drawBitmap(clefSource, null, clefRect, null);
canvas.drawBitmap(source, rect, rect2, null);
}
So with that code i can show a portion of the notes drawable, after converting it to a Bitmap. And i can also draw both of them, and the horizontal position is aligned. The problem is that the vertical position is not aligned, what i'm getting is:
So i know that my code is not correct (i'm pretty new to canvas in android and trying to figure out what to do), and what i learned so far is:
that in order to select a portion of the image i need to convert it to the Bitmap (i haven't found any way to do it directly with the VectorDrawable)
While drawing a Bitmap on the canvas with DrawBitmap, the first Rect represents the portion area i want to show, and the second one is the size and position of the area displayed.
In order to have the bitmap displayed on the canvas, i need to create a canvas from the Bitmap and draw it in it, in order to have it displayed. Is that correct?
So i have several questions:
I would like to understand how to vertically align the images, so they have to start from the same y (top).
I'm not sure if the vector image is the best idea, maybe is better to convert it into display dependant pngs? Or anyway the canvas size is relative to the screen? Or maybe i need to make my code screen-independent (i suppose that getIntrinsicWidth/Height are returning the real size of the image, so maybe i need to scale it?)
Why I need to explicitly setBounds of both images to have them displayed?
UPDATE #1
So i understood why probably my images are not aligned on the same line. It looks like that when creating a vector asset, for some reason the sizes are "adapted", not sure if is the android systems doing that or android studio. But anyway what i found after loading two images with the same height in pixels, is that for one i have an height, and for the other i have a different height (nearly double), and that explain why the image is shifted on the bottom.
So what i tried is to make a single image with both the notes, and the clefs, and it sort of works in the emulator. But when testing on a real device i get the error:
W/OpenGLRenderer: Bitmap too large to be uploaded into a texture (11732x1168, max=8192x8192)
Bitmap too large to be uploaded into a texture (11732x1168, max=8192x8192)
i can understand what the error means, but anyway the image size in pixel is: 2933x292 pixels. Why the getIntrinsicWidth and getIntrinsicHeight are returning that dimensions? what is their metrics?
I'm wondering that maybe the vector drawable is not the best choice? Maybe is better to cnvert it into screen-dependant pngs? and use them?

Crop bottom portion of a bitmap programmatically

I have a bitmap taken from a camera. I want to crop the image so it only leaves the bottom portion of it. The cropped image should be 80% less the height of the original bitmap, so I want only the 20% of the bottom part starting from the left edge.
I'm doing this explicitly in the code without any Android cropping intent whatsoever.
An image to visualize what I want to achieve:
I've managed to crop the top part of the bitmap by using this code:
final Bitmap toBeCropped = BitmapFactory.decodeFile(mFile.getPath());
final BitmapFactory.Options bitmapOptions = new BitmapFactory.Options();
bitmapOptions.inTargetDensity = 1;
toBeCropped.setDensity(Bitmap.DENSITY_NONE);
int fromHere = (int) (toBeCropped.getHeight() * 0.2);
Bitmap croppedBitmap = Bitmap.createBitmap(toBeCropped, 0, 0, toBeCropped.getWidth(), fromHere);
mPreviewHalf.setImageBitmap(croppedBitmap);
But I couldn't find a way to start the cropping 80% from the top. I'm thinking of getting the y-coordinate of the Bitmap, so that I could crop any image sizes and always get the bottom portion only. But can anyone point to me how do I get this coordinate from a bitmap? Or do I have to take it from the layout itself?

I am not familiar with operations on Bitmaps but from inspecting your code and looking at the API my guess would be that you need to specify the y coordinates on the following line to match the starting point:
Bitmap croppedBitmap = Bitmap.createBitmap(toBeCropped, 0, "here", toBeCropped.getWidth(), fromHere);
So my guess would be something like the following:
Bitmap croppedBitmap = Bitmap.createBitmap(toBeCropped, 0, (toBeCropped.getHeight() * 0.8), toBeCropped.getWidth(), fromHere);
in this case fromHere will define the number of rows you want to crop not the starting point (which is 20% of the total as you have pointed out)

This is how I do it:
topcutoff is what you want to cut of on top of the image and buttomcutoff on the buttom (if needed)
height = height - topcutoff;
height = height - bottomcutoff;
croppedBitmap = Bitmap.createBitmap(croppedBitmap, 0, topcutoff, width, height);
Basically you just set a startpoint (topcutoff) from where to begin displaying the bitmap. In your case this would be the position after 80% of your bitmap.
This might also explain some things: Google Bitmap Documentation
"int: The y coordinate of the first pixel in source", so where you want to begin displaying your image.

Using a rounded corners drawable

There is a nice post made by the popular Google developer Romain Guy that shows how to use a rounded corners drawable (called "StreamDrawable" in his code ) on a view efficiently.
The sample itself works very well on my Galaxy S3 when in portrait mode, but I have a few issues with it:
if the screen is small (for example on qvga screens), the shown images get cropped.
if I have an input bitmap that is too small than how I wish to show it, the output image has its edges smeared. Even on the Galaxy S3, when you run the sample code and it's on landscape, it looks awful:
I'm still not sure about it (since I use a workaround of scaling the image for using the sample code), but it think that even this solution is a bit slow when being used in a listView. Maybe there is a renderscript solution for this?
It doesn't matter if I use setImageDrawable or setBackgroundDrawable. It must be something in the drawable itself.
I've tried to play with the variables and the bitmapShader, but nothing worked. Sadly TileMode doesn't have a value for just stretching the image, only tiling it in some way.
As a workaround I can create a new scaled bitmap, but it's just a workaround. Surely there is a better way which will also not use more memory than it should.
How do I fix those issues and use this great code?

I think that the solution that is presented on this website works well.
unlike other solutions, it doesn't cause memory leaks, even though it is based on Romain Guy's solution.
EDIT: now on the support library, you can also use RoundedBitmapDrawable (using RoundedBitmapDrawableFactory ) .

I had some size issues with this code, and I solved it.
Maybe this will help you, too:
1) in the constructor store the bitmap in a local variable (e.g. private Bitmap bmp;)
2) override two more methods:
#Override
public int getIntrinsicWidth() {
return bmp.getWidth();
}
#Override
public int getIntrinsicHeight() {
return bmp.getHeight();
}
Best regards,
DaRolla

There underlying problem is that the BitmapShader's TileMode doesn't have a scaling option. You'll note in the source that it's been set to Shader.TileMode.CLAMP, and the docs describe that as:
replicate the edge color if the shader draws outside of its original bounds
To work around this, there are three solutions:
Constrain the size of the view in which the drawable is used to the size of the bitmap.
Constrain the drawing region; for instance, change:
int width = bounds.width() - mMargin;
int height = bounds.height() - mMargin;
mRect.set(mMargin, mMargin, width, height);
To:
int width = Math.min(mBitmap.getWidth(), bounds.width()) - mMargin;
int height = Math.min(mBitmap.getHeight(), bounds.height()) - mMargin;
mRect.set(mMargin, mMargin, width, height);
Scale the bitmap to the size of the drawable. I've moved creating the shader into onBoundsChange() and have opted to create a new bitmap from here:
bitmap = Bitmap.createScaledBitmap(mBitmap, width, height, true);
mBitmapShader = new BitmapShader(bitmap,
Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
Note that this a potentially slow operation and will be running on the main thread. You might want to carefully consider how you want to implement it before you go for this last solution.

Android Drawable looks ugly due to scaling

I am writing a View that should show a drawable that seems to "never end".
It should be twice or third the displaysize and move slow through the display.
Therefore I studied some samplecode by Google and found the important Lines
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
canvasWidth = width;
canvasHeight = height;
float sf = backgroundImage.getWidth() / canvasWidth;
backgroundImage = Bitmap.createScaledBitmap(backgroundImage,
(int) (canvasWidth * sf), canvasHeight, true);
}
To rescale the image and than
// decrement the far background
backgroundXPos = backgroundXPos - DELTAMOVE;
// calculate the wrap factor for matching image draw
int newFarX = backgroundImage.getWidth() - (-backgroundXPos);
// if we have scrolled all the way, reset to start
if (newFarX <= 0) {
backgroundXPos = 0;
// only need one draw
canvas.drawBitmap(backgroundImage, backgroundXPos, 0, null);
} else {
// need to draw original and wrap
canvas.drawBitmap(backgroundImage, backgroundXPos, 0, null);
canvas.drawBitmap(backgroundImage, newFarX, 0, null);
}
To draw the moving image. The images is already moving, it's fine.
But, and this is the point of my question, the image looks very ugly. Its original is 960*190 pixels by 240ppi. It should be drawn inside a view with 80dip of height and "fill_parent" width.
It should look same (and good) on all devices. I have tried a lot but I don't know how to make the picture look nice.
Thanks for your help.
Best regards,
Till

Since you're saying that it's a never ending drawable, probably you're writing a game of some sort. If your image is a pixel-art type, then you don't want any scaling; pixel-art-type images cannot be scaled and keep its crisp look (you can try using nearest neighbor interpolation and scaling to an integer multiple of the original, which sometimes might work, but sometimes you will still need manual tweaks). This is the rare case where you actually would need to have different image resource for different screen resolutions.
Otherwise you might want to use a vector image, but if -- as you said -- your original is a high resolution image, then vector image probably won't help much here.
btw, you probably want to show some screenshot. "Looks ugly" is just as helpful as saying my code does not work.

Just a guess, but instead of passing a null paint to your drawBitmap() calls, try making a paint with bitmap filtering disabled:
Paint p = new Paint();
p.setFilterBitmap(false);
canvas.drawBitmap(backgroundImage, backgroundXPos, 0, p);
Hope that helps.

Drawing subset of a bitmap to a canvas?

I'm writing my first app of any consequence, so I may be going about this the entire wrong way, but...
I have a resource image that is 1600x880. I'd like to fill the entire screen with a subset of that image to my canvas, such that an arbitrary x,y coordinate marks the top-left corner drawn at the top-left corner of the screen. For instance, if I was viewing this image on an N1 and I entered x=100 and y=50, I'd expect to see from 100,50 to 580,850 since it's display area is 480x800.
I think I need to use Canvas.drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint). But, no matter what I plug in to either Rect (even if it's a perfectly sane set of values that shouldn't butt up against any edges of the image), I end up with an unexpected area or a grossly stretched/smooshed output.
I've tried using various combinations of calculations involving display.getWidth() and getHeight(), canvas.getWidth() and getHeight(), and bitmap.getWidth() and getHeight() but nothing seems to be working.
I don't know what I'm doing wrong.