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?

Android Canvas not drawing more than screen dimensions

My App have a feature that let's the user capture photo and add drawing on that photo.
All the photo's are re-sized to exactly 900 x 900.
To allow the user add drawing to the image. I keep a transparent image over the original image and do the drawing on the transparent image. Drawing is done using canvas.
But when drawing in a device that has 720 x 480 (height x width). If i create a 900 x 900 transparent image and draw a line from 0,0 to 900,900, canvas only draws line from 0,0 to 480,480.
Below is the respective portion of the code:
Preparing Canvas:
holder = getHolder();
if (holder.getSurface().isValid()) {
Canvas canvas = holder.lockCanvas();
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
/* original image is 900 x 900 */
overlayBitmap = Bitmap.createBitmap(originalImage.getWidth(), originalImage.getHeight(), originalImage.getConfig());
canvas.setBitmap(overlayBitmap);
}
Drawing Line:
canvas.drawLine(0, 0, 900, 900, paint);
I have no idea why i am having this issue. It is because of using canvas?? Is there any work around? Any help is highly appreciated :-)

After some more reading about canvas and also help from this post i was able to fix the issue.
The issue was in the canvas clip rectangle. It was (0,0,480,480) by default as device display was 720 x 480 i guess? So whatever was on the bitmap was always clipped down to 480 x 480.
Later i modified my code like this:
holder = getHolder();
if (holder.getSurface().isValid()) {
Canvas canvas = holder.lockCanvas();
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
/* original image is 900 x 900 */
overlayBitmap = Bitmap.createBitmap(originalImage.getWidth(), originalImage.getHeight(), originalImage.getConfig());
canvas.setBitmap(overlayBitmap);
/* set extended clip rectangle for the larger target bitmap */
Rect clipRect = canvas.getClipBounds();
clipRect.set(0, 0, image.getWidth(), image.getHeight());
canvas.clipRect(clipRect, Region.Op.REPLACE);
}
After replacing clip rectangle size with image size everything worked just fine.

Just because a photo is 900x900, that doesn't mean that it's exactly those many pixels when displayed on the device screen. Device screens can have very different sizes, and when an image (or any view for that matter) is told to expand its with to fit the screen, or measured in dp (device independent pixels), the actual number of device pixels will vary depending on the device screen.
Your code needs to be sensitive to these differences. When you do your drawing, don't assume the size of the Canvas of a view. Instead, ask the view how big it is, and perform all the drawing based on the actual measured size.

How do I scale a 8x8 pixel art Bitmap to be 100 pixels width and height without any distortion in Android?

I'm making a game that is Pixel-based in Android. I have several 8x8 sprites that need to be resized to fit on a 100x100 area. As a test to see if it would work, I tried to just make the image fill the entire canvas. It kind of worked, but it made the 8x8 sprite turn into a 12x12 sprite, making the pixels look really odd and distorted. Here's what I have so far:
Bitmap grass = BitmapFactory.decodeResource(getResources(), R.drawable.small);
Paint configuration = new Paint();
configuration.setDither(false);
configuration.setAntiAlias(false);
Matrix myMatrix = new Matrix();
myMatrix.postScale(canvas.getWidth() / grass.getWidth(), canvas.getWidth() / grass.getHeight());
Bitmap resizedBitmap = Bitmap.createBitmap(grass, 0, 0, grass.getWidth(), grass.getHeight(), myMatrix, false);
canvas.drawBitmap(resizedBitmap, 0, 0, null);

If you work on bitmaps then you simply can't. You'd minimize the distortion by scaling up by non-fractional factor so each pixed would be repeated same number of times (i.e. image 10x10 to 20x20 is scaled by factor of two, but 8x8 to 12x12 is 1,5 so no luck). The solution would be to have all assets in vector form (i.e. SVG) and then render them on run-time according to device density and other specs or prepare separate assets for various type of devices (which would blow application size up a bit)

How to scale bitmaps on View.Canvas in Android?

I have a View-derived class where I draw a 790x500 (yes, this is odd but it has to stay this way) bitmap directly on the canvas in onDraw. This looks ok on my Nexus S, but when I run my app on a device with a smaller screen (e.g. Wildfire) I only see the upper left part of the bitmap. What am I missing here?
This is a game-like app where I draw a number of bitmaps on certain coordinates. I really don't want to have different pixel setups for LDPI, MDPI and HDPI (I have a good reason for this).
Q: How can I properly scale my bitmaps for any screen resolution? (Centering the game screen for large screens may be an option, but is not a must.) E.g. when I draw a 800x600 image on a 320x240 screen, the image is automatically stretched and when I output a pixel at 100x100, it becomes 40x40.

There are many forms of the drawbitmap() method. Choose the one that allows you to specify the source and destination rectangle. The source rectangle will be the size of your bitmap and the destination rectangle will be scaled to fit on the device display. Android will scale your bitmap when it draws it.
Rect rs = new Rect();
Rect rd = new Rect();
rs.left = rs.top = 0;
rs.right = 789;
rs.bottom = 499;
<calculate destination rectangle from device size>
canvas.drawBitmap(myBitmap, rs, rd, null);
You can also scale and translate (shift) the entire canvas
canvas.scale(float scaleX, float scaleY);
canvas.translate(float dx, float dy);

Canvas.scale() does the trick.

How to increase Canvas size in Android?

Is there anyway to increase Canvas size more then my screen size in Android? Like if my screen size is 320 x 480 I want to increase my canvas size 3 times bigger then that.

You can create a bitmap of desired size and then draw needed part of it to canvas using drawBitmap (Bitmap bitmap, Rect src, Rect dst, Paint paint) method of canvas.