Develop Reference

Canvas.drawText slow when scaling animation

I built a zoomable, scrollable view, based on this demo. I have text in each cell. It works fine, but when the user zooms, the animation is lagged. I found the culprit: it is Canvas.drawText, without it, the Rect drawings are just running smooth.
This is the code snippet for drawing, with some psuedo-code:
#Override
protected void onDraw(Canvas canvas) {
float scale = VISIBLE_NUM_COLUMNS / mCurrentViewport.width();
float rectWidth = 1.f / mFactor * scale - 1;
float strokeWidth = scale * 1.f < 1.f ? 0 : scale * 1.f;
mBorderPaint.setStrokeWidth(strokeWidth);
mFontPaint.setTextSize(scale * TEXT_SIZE);
for (int i = first_visible_row; i < all_rows && i <= last_row; ++i) {
for (int j = first_visiblecolumn; j < all_columns && j <= last_visible_column; ++j) {
float rectLeft = getDrawX(j);
float rectTop = getDrawY(i);
// drawing the rect
float rectCenterX = rectLeft + rectWidth / 2;
float rectCenterY = rectTop + rectWidth / 2;
canvas.drawText(actual_text, rectCenterX, rectCenterY + -(mFontMetricsBuffer.ascent), mFontPaint);
}
}
}
...
#Override
public boolean onScale(ScaleGestureDetector scaleGestureDetector) {
// calculate new viewport
if (!awakenScrollBars()) {
ViewCompat.postInvalidateOnAnimation(MyView.this);
}
}
Is there any way to speed up the text drawing?

Android Bitmap remove white margin

I've got a question regarding Bitmaps in Android: I 've got a Bitmap with white margins [size unknown] around. Is it possible to create a new Bitmap with all the white margins removed (rectangular shape)?
Bitmap bmp = Bitmap.createBitmap(width, bmpheigth, Config.ARGB_8888);
Canvas canvas = new Canvas(bmp);
canvas.setBitmap(bmp);
canvas.drawColor(Color.WHITE);
// draw here things!
It is asumed to be unknown where are things painted.
What is a good way to do that?
thanks!

Thanks #Maxim Efimov & #StackOverflowException
Just in Case Someone will need a snippet for this kind of problems:
this method returns a cut out smaller Bitmap with Margins removed. passing the pixels to a int-array first and then working with the array is a bit faster than the Bitmap.getPixel method
just call the method indicating Source Bitmap and Background color.
Bitmap bmp2 = removeMargins(bmp, Color.WHITE);
private static Bitmap removeMargins2(Bitmap bmp, int color) {
// TODO Auto-generated method stub
long dtMili = System.currentTimeMillis();
int MTop = 0, MBot = 0, MLeft = 0, MRight = 0;
boolean found1 = false, found2 = false;
int[] bmpIn = new int[bmp.getWidth() * bmp.getHeight()];
int[][] bmpInt = new int[bmp.getWidth()][bmp.getHeight()];
bmp.getPixels(bmpIn, 0, bmp.getWidth(), 0, 0, bmp.getWidth(),
bmp.getHeight());
for (int ii = 0, contX = 0, contY = 0; ii < bmpIn.length; ii++) {
bmpInt[contX][contY] = bmpIn[ii];
contX++;
if (contX >= bmp.getWidth()) {
contX = 0;
contY++;
if (contY >= bmp.getHeight()) {
break;
}
}
}
for (int hP = 0; hP < bmpInt[0].length && !found2; hP++) {
// looking for MTop
for (int wP = 0; wP < bmpInt.length && !found2; wP++) {
if (bmpInt[wP][hP] != color) {
Log.e("MTop 2", "Pixel found #" + hP);
MTop = hP;
found2 = true;
break;
}
}
}
found2 = false;
for (int hP = bmpInt[0].length - 1; hP >= 0 && !found2; hP--) {
// looking for MBot
for (int wP = 0; wP < bmpInt.length && !found2; wP++) {
if (bmpInt[wP][hP] != color) {
Log.e("MBot 2", "Pixel found #" + hP);
MBot = bmp.getHeight() - hP;
found2 = true;
break;
}
}
}
found2 = false;
for (int wP = 0; wP < bmpInt.length && !found2; wP++) {
// looking for MLeft
for (int hP = 0; hP < bmpInt[0].length && !found2; hP++) {
if (bmpInt[wP][hP] != color) {
Log.e("MLeft 2", "Pixel found #" + wP);
MLeft = wP;
found2 = true;
break;
}
}
}
found2 = false;
for (int wP = bmpInt.length - 1; wP >= 0 && !found2; wP--) {
// looking for MRight
for (int hP = 0; hP < bmpInt[0].length && !found2; hP++) {
if (bmpInt[wP][hP] != color) {
Log.e("MRight 2", "Pixel found #" + wP);
MRight = bmp.getWidth() - wP;
found2 = true;
break;
}
}
}
found2 = false;
int sizeY = bmp.getHeight() - MBot - MTop, sizeX = bmp.getWidth()
- MRight - MLeft;
Bitmap bmp2 = Bitmap.createBitmap(bmp, MLeft, MTop, sizeX, sizeY);
dtMili = (System.currentTimeMillis() - dtMili);
Log.e("Margin 2",
"Time needed " + dtMili + "mSec\nh:" + bmp.getWidth() + "w:"
+ bmp.getHeight() + "\narray x:" + bmpInt.length + "y:"
+ bmpInt[0].length);
return bmp2;
}

Use Bitmap.createBitmap(source, x, y, width, height) so knowing the white margin size you can do what you want.

My solution:
private Bitmap trim(Bitmap bitmap, int trimColor){
int minX = Integer.MAX_VALUE;
int maxX = 0;
int minY = Integer.MAX_VALUE;
int maxY = 0;
for(int x = 0; x < bitmap.getWidth(); x++){
for(int y = 0; y < bitmap.getHeight(); y++){
if(bitmap.getPixel(x, y) != trimColor){
if(x < minX){
minX = x;
}
if(x > maxX){
maxX = x;
}
if(y < minY){
minY = y;
}
if(y > maxY){
maxY = y;
}
}
}
}
return Bitmap.createBitmap(bitmap, minX, minY, maxX - minX + 1, maxY - minY + 1);
}
It isn't very fast, for 1280 x 576 px bitmap execution took 2965ms on Xiaomi Redmi 3S.
If it possible scale down image before triming:
private Bitmap scaleDown(Bitmap bitmap, float maxImageSize, boolean filter) {
float ratio = Math.min(maxImageSize / bitmap.getWidth(), maxImageSize / bitmap.getHeight());
int width = Math.round(ratio * bitmap.getWidth());
int height = Math.round(ratio * bitmap.getHeight());
return Bitmap.createScaledBitmap(bitmap, width, height, filter);
}

Late to the party, but this variation is a bit faster and perhaps easier to read:
public static Bitmap imageWithMargin(Bitmap bitmap, int color, int maxMargin) {
int maxTop = 0, maxBottom = 0, maxLeft = 0, maxRight = 0;
int width = bitmap.getWidth();
int height = bitmap.getHeight();
int[] bitmapArray = new int[width * height];
bitmap.getPixels(bitmapArray, 0, width, 0, 0, width, height);
// Find first non-color pixel from top of bitmap
searchTopMargin:
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
if (bitmapArray[width * y + x] != color) {
maxTop = y > maxMargin ? y - maxMargin : 0;
break searchTopMargin;
}
}
}
// Find first non-color pixel from bottom of bitmap
searchBottomMargin:
for (int y = height - 1; y >= 0; y--) {
for (int x = width - 1; x >= 0; x--) {
if (bitmapArray[width * y + x] != color) {
maxBottom = y < height - maxMargin ? y + maxMargin : height;
break searchBottomMargin;
}
}
}
// Find first non-color pixel from left of bitmap
searchLeftMargin:
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
if (bitmapArray[width * y + x] != color) {
maxLeft = x > maxMargin ? x - maxMargin : 0;
break searchLeftMargin;
}
}
}
// Find first non-color pixel from right of bitmap
searchRightMargin:
for (int x = width - 1; x >= 0; x--) {
for (int y = height - 1; y >= 0; y--) {
if (bitmapArray[width * y + x] != color) {
maxRight = x < width - maxMargin ? x + maxMargin : width;
break searchRightMargin;
}
}
}
return Bitmap.createBitmap(bitmap, maxLeft, maxTop, maxRight - maxLeft, maxBottom - maxTop);
}

How to display a class which extends view class inside horizontal scroll view...?

I have created bar chart for my application, but my bar chart is not scroll-able, so I have added my liner layout into horizontal scroll view..
Here is my xml file is...
<?xml version="1.0" encoding="utf-8"?>
<HorizontalScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/horizaontalforscroll">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/linearforscroll" >
</LinearLayout>
Here I'm calling MyGraph class which extends View class..
LinearLayout linear=(LinearLayout) findViewById(R.id.linearforscroll);
MyGraph graph = new MyGraph(this);
linear.addView(graph);
HorizontalScrollView hr = (HorizontalScrollView)findViewById(R.id.horizaontalforscroll);
hr.removeAllViewsInLayout();
hr.addView(linear);
Add finally my MyGraph class..
public class MyGraph extends View{
private static final int SHAPE_WIDTH = 10;
private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
public MyGraph(Context context) {
// TODO Auto-generated constructor stub
super(context);
}
#Override
protected void onDraw(Canvas canvas){
// TODO Auto-generated method stub
super.onDraw(canvas);
paint.setStyle(Style.FILL);
int legendSize = 0;
if(legendSize == 0){
legendSize = height / 5;
}
int[] margine = new int[]{40,30,20,200,250};
int startX = x + margine[0];
int startY = y;
int stopX = x + margine[0];
int stopY = 0;
Log.d("JWP", "W & H:"+width+":"+height);
if(width < height){
stopY = y + height - margine[4];
}
else{
stopY = y + height - margine[3];
}
int length = values.length;
paint.setColor(Color.WHITE);
canvas.drawLine(startX, startY, stopX, stopY, paint);
canvas.drawLine(stopX, stopY, x + width, stopY, paint);
int rHeight = stopY;
for(int i = 0;i < length; i++){
double percentage = (values[i]*rHeight)/maxValue;
Log.d("JWP", "Values:"+values[i]);
Log.d("JWP", "PERCENTAGE:"+percentage);
paint.setColor(COLORS[(i) % COLORS.length]);
int modifiedStratY = rHeight - (int) percentage + 20;
if(modifiedStratY > rHeight){
modifiedStratY = rHeight - (int) percentage;
}
canvas.drawRect(startX, modifiedStratY, startX+30, rHeight, paint);
paint.setTextSize(15);
canvas.drawText(String.valueOf(values[i]), startX, modifiedStratY, paint);
canvas.save();
canvas.rotate(35, startX, rHeight + 7);
paint.setColor(Color.WHITE);
paint.setTextSize(13);
canvas.drawText(name[i], startX, rHeight + 7, paint);
canvas.restore();
startX += 70;
}
String xTitle = "Directory Name";
int xTitleLength = xTitle.length()/2;
int xTitleStart = (x + width/2) - xTitleLength/2;
paint.setTextSize(15);
canvas.drawText(xTitle, xTitleStart,y + rHeight + 65, paint);
String yTitle = "Amount of Space in MB";
int yTitleLength = yTitle.length();
int yTitleStart = (y + rHeight/2) + yTitleLength*2;
canvas.save();
canvas.rotate(-90, x + 10 , yTitleStart);
canvas.drawText(yTitle, x + 10, yTitleStart, paint);
canvas.restore();
paint.setTextSize(12);
canvas.drawText(String.valueOf(maxValue), x + 12, y + 20, paint);
canvas.drawText("0.0", x + 11, rHeight, paint);
float yLabelValue = (float) maxValue / 4;
int yLabelPoints = rHeight / 4;
canvas.drawText(String.valueOf(yLabelValue*3), x + 12, (rHeight - yLabelPoints*3 + 20), paint);
for(int j = 1; j < 3; j++){
canvas.drawText(String.valueOf(yLabelValue), x + 12, (rHeight - yLabelPoints + 20), paint);
yLabelPoints += yLabelPoints;
yLabelValue += yLabelValue;
}
int left = x + 15;
int right = x + width - 5;
String[] title = new String[length];
for(int i = 0; i < length; i++){
title[i] = name[i];
}
drawLegends(canvas,title,left,right,y,width,height,legendSize,paint);
}
}
My query is, when I run run the code nothing is displayed on screen, if I run without horizontal scroll view result is displayed clearly..
Please help me to solve the issue..
Thank you.

Change
LinearLayout linear=(LinearLayout) findViewById(R.id.linearforscroll);
MyGraph graph = new MyGraph(this);
linear.addView(graph);
HorizontalScrollView hr = (HorizontalScrollView)findViewById(R.id.horizaontalforscroll);
hr.removeAllViewsInLayout();
hr.addView(linear);
to:
LinearLayout linear=(LinearLayout) findViewById(R.id.linearforscroll);
linear.removeAllViewsInLayout();
MyGraph graph = new MyGraph(this);
linear.addView(graph);

Is it possible to remove transparent pixels from bitmap in android

In my application i am taking screenshot if the image doesn't fill imageView then transparent pixels are added to bitmap.Is it possible to remove transparent pixels from bitmap or take screenshot without transparent pixels.Thanks in advance.

This method is a lot faster:
static Bitmap trim(Bitmap source) {
int firstX = 0, firstY = 0;
int lastX = source.getWidth();
int lastY = source.getHeight();
int[] pixels = new int[source.getWidth() * source.getHeight()];
source.getPixels(pixels, 0, source.getWidth(), 0, 0, source.getWidth(), source.getHeight());
loop:
for (int x = 0; x < source.getWidth(); x++) {
for (int y = 0; y < source.getHeight(); y++) {
if (pixels[x + (y * source.getWidth())] != Color.TRANSPARENT) {
firstX = x;
break loop;
}
}
}
loop:
for (int y = 0; y < source.getHeight(); y++) {
for (int x = firstX; x < source.getWidth(); x++) {
if (pixels[x + (y * source.getWidth())] != Color.TRANSPARENT) {
firstY = y;
break loop;
}
}
}
loop:
for (int x = source.getWidth() - 1; x >= firstX; x--) {
for (int y = source.getHeight() - 1; y >= firstY; y--) {
if (pixels[x + (y * source.getWidth())] != Color.TRANSPARENT) {
lastX = x;
break loop;
}
}
}
loop:
for (int y = source.getHeight() - 1; y >= firstY; y--) {
for (int x = source.getWidth() - 1; x >= firstX; x--) {
if (pixels[x + (y * source.getWidth())] != Color.TRANSPARENT) {
lastY = y;
break loop;
}
}
}
return Bitmap.createBitmap(source, firstX, firstY, lastX - firstX, lastY - firstY);
}

I have done this way and it works great.
public static Bitmap createTrimmedBitmap(Bitmap bmp) {
int imgHeight = bmp.getHeight();
int imgWidth = bmp.getWidth();
int smallX=0,largeX=imgWidth,smallY=0,largeY=imgHeight;
int left=imgWidth,right=imgWidth,top=imgHeight,bottom=imgHeight;
for(int i=0;i<imgWidth;i++)
{
for(int j=0;j<imgHeight;j++)
{
if(bmp.getPixel(i, j) != Color.TRANSPARENT){
if((i-smallX)<left){
left=(i-smallX);
}
if((largeX-i)<right)
{
right=(largeX-i);
}
if((j-smallY)<top)
{
top=(j-smallY);
}
if((largeY-j)<bottom)
{
bottom=(largeY-j);
}
}
}
}
Log.d(TAG, "left:" + left + " right:" + right + " top:" + top + " bottom:" + bottom);
bmp=Bitmap.createBitmap(bmp,left,top,imgWidth-left-right, imgHeight-top-bottom);
return bmp;
}

Bitmap imageWithBG = Bitmap.createBitmap(image.getWidth(), image.getHeight(),image.getConfig()); // Create another image the same size
imageWithBG.eraseColor(Color.WHITE); // set its background to white, or whatever color you want
Canvas canvas = new Canvas(imageWithBG); // create a canvas to draw on the new image
canvas.drawBitmap(image, 0f, 0f, null); // draw old image on the background
image.recycle(); // clear out old image

To trim crop transparent borders of a image in Android you ca use
this arrange. Work faster because don't need read all pixels, it just slice the bitmap, more details: CropTrimTransparentImage
public Bitmap crop (Bitmap bitmap){
int height = bitmap.getHeight();
int width = bitmap.getWidth();
int[] empty = new int[width];
int[] buffer = new int[width];
Arrays.fill(empty,0);
int top = 0;
int left = 0;
int botton = height;
int right = width;
for (int y = 0; y < height; y++) {
bitmap.getPixels(buffer, 0, width, 0, y, width, 1);
if (!Arrays.equals(empty, buffer)) {
top = y;
break;
}
}
for (int y = height - 1; y > top; y--) {
bitmap.getPixels(buffer, 0, width, 0, y, width, 1);
if (!Arrays.equals(empty, buffer)) {
botton = y;
break;
}
}
int bufferSize = botton -top +1;
empty = new int[bufferSize];
buffer = new int[bufferSize];
Arrays.fill(empty,0);
for (int x = 0; x < width; x++) {
bitmap.getPixels(buffer, 0, 1, x, top + 1, 1, bufferSize);
if (!Arrays.equals(empty, buffer)) {
left = x;
break;
}
}
for (int x = width - 1; x > left; x--) {
bitmap.getPixels(buffer, 0, 1, x, top + 1, 1, bufferSize);
if (!Arrays.equals(empty, buffer)) {
right = x;
break;
}
}
Bitmap cropedBitmap = Bitmap.createBitmap(bitmap, left, top, right-left, botton-top);
return cropedBitmap;
}

How do I draw a graph on Android without using any external API? [closed]

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I understand how to draw lines using a canvas, but how can I use the same lines using a canvas to draw a graph?
The problem is with the coordinates. (0,0) starts right at the top left corner of the device. How can I set (0,0) as the margin and draw the particular line with respect to the margin?

1)Create an activity.
public class GraphView1 extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
float[] values = new float[] { "your values"};
String[] verlabels = new String[] { "your values" };
String[] horlabels = new String[] { "your values"
GraphView graphView = new GraphView(this, values,"GraphView",horlabels, verlabels, GraphView.BAR);
setContentView(graphView);
}
}
2)Then create another class extends View:
public class GraphView2 extends View{
public static boolean LINE = true;
private Paint paint;
private float[] values;
private String[] str;
private String[] verlabels;
private String title;
private boolean type;
Context context;
public GraphView(Context context, float[] values, String title, String[] str,String[] verlabels, boolean type) {
super(context);
if (values == null)
values = new float[0];
else
this.values = values;
if (title == null)
title = "";
else
this.title = title;
if (str == null)
this.str = new String[0];
else
this.str = str;
if (verlabels == null)
this.verlabels = new String[0];
else
this.verlabels = verlabels;
this.type = type;
paint = new Paint();
}
#Override
protected void onDraw(final Canvas canvas) {
context=getContext();
float border = 15;
float horstart = border * 2;
float height = getHeight();
float width = getWidth();
float max = getMax();
Log.w("max", ""+max);
float min = getMin();
Log.w("min", ""+min);
float diff = max - min;
float graphheight = height - (2 * border);
float graphwidth = width - (2 * border);
paint.setTextAlign(Align.LEFT);
int vers = verlabels.length;
for (int i = 0; i < verlabels.length; i++) {
paint.setColor(Color.DKGRAY);
float y = ((graphheight / vers) * i) + border;
canvas.drawLine(horstart, y, width, y, paint);
paint.setColor(Color.WHITE);
paint.setTextSize(10);
canvas.drawText(verlabels[i], 0, y, paint);
}
int hors = values.length;
for (int i = 0; i < str.length; i++) {
paint.setColor(Color.DKGRAY);
float x = ((graphwidth / hors) * i) + horstart;
canvas.drawLine(x, height - border, x, border, paint);
paint.setTextAlign(Align.LEFT);
if (i==str.length)
paint.setTextAlign(Align.RIGHT);
if (i==0)
paint.setTextAlign(Align.LEFT);
paint.setColor(Color.WHITE);
paint.setTextSize(9);
canvas.drawText( str[i], x, height - 4, paint);
}
paint.setTextAlign(Align.CENTER);
canvas.drawText(title, (graphwidth / 2) + horstart, border - 4, paint);
if (max != min) {
paint.setColor(Color.BLUE);
paint.setStyle(Paint.Style.FILL);
if (type == BAR) {
float datalength = values.length;
float colwidth = (width - (2 * border)) / datalength;
for (int i = 0; i < values.length; i++) {
// float val = values[i] - min;
// float rat = val / diff;
// float h = graphheight * rat;
// canvas.drawRect((i * colwidth) + horstart, (border - h) + graphheight, ((i * colwidth) + horstart) + (colwidth - 1), height - (border - 1), paint);
float graph_h = getHeight()-(border*2);
// Log.e("", "graph_h > "+graph_h);
float ind_h = graph_h/7;
//Log.e("", "ind_h > "+ind_h);
float t = values[i]/5;
float top = (graph_h - ind_h*(t));
// Log.e("", " > "+i+1);
// Log.e("", "top > "+top);
//for values between 0 and 5 ,vice versa
//Log.e("", " values[i] > "+values[i]);
float acc = ind_h/5;
acc = acc * (values[i]%5);
// Log.e("", " acc > "+acc);
canvas.drawRect((i * colwidth) + horstart, top+border-acc , ((i * colwidth) + horstart) + (colwidth - 1), graph_h+border, paint);
}
} else {
float datalength = values.length;
float colwidth = (width - (2 * border)) / datalength;
float halfcol = colwidth / 2;
float lasth = 0;
for (int i = 0; i < values.length; i++) {
float val = values[i] - min;
float rat = val / diff;
float h = graphheight * rat;
if (i > 0)
canvas.drawLine(((i - 1) * colwidth) + (horstart + 1) + halfcol, (border - lasth) + graphheight, (i * colwidth) + (horstart + 1) + halfcol, (border - h) + graphheight, paint);
lasth = h;
}
}
}
}
private float getMax() {
float largest = Integer.MIN_VALUE;
for (int i = 0; i < values.length; i++)
if (values[i] > largest)
largest = values[i];
return largest;
}
private float getMin() {
float smallest = Integer.MAX_VALUE;
for (int i = 0; i < values.length; i++)
if (values[i] < smallest)
smallest = values[i];
return smallest;
}
}