CanvasView

Android Application Library

Overview

This library defines API for drawing application.

Usage

Application creates layout XML and Activity for using this library.
For example,

activity_draw.xml

...

<com.android.graphics.CanvasView
    android:id="@+id/canvas"
    android:layout_width="280dp"
    android:layout_height="280dp"
    android:layout_gravity="center_horizontal" />

...

DrawActivity.java

// ...

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.android.graphics.CanvasView;

public class DrawActivity extends AppCompatActivity {

    private CanvasView canvas = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_draw);

        this.canvas = (CanvasView)this.findViewById(R.id.canvas);
    }

    // ...
}

Creating XML and Activity enables to draw on canvas.

API

Undo / Redo / Clear

this.canvas.undo();   // Undo
this.canvas.redo();   // Redo
this.canvas.clear();  // Clear canvas

Mode

The application that use this library has 3 states.

// Setter
this.canvas.setMode(CanvasView.Mode.DRAW);    // for drawing
this.canvas.setMode(CanvasView.Mode.TEXT);    // for drawing Text
this.canvas.setMode(CanvasView.Mode.ERASER);  // for using Eraser

// Getter
CanvasView.Mode mode = this.canvas.getMode();

Drawer

This libarary enable to draw Figures.

// Setter
this.canvas.setDrawer(CanvasView.Drawer.PEN);               // Use Pen Tool
this.canvas.setDrawer(CanvasView.Drawer.LINE);              // Draw Line
this.canvas.setDrawer(CanvasView.Drawer.RECTANGLE);         // Draw Rectangle
this.canvas.setDrawer(CanvasView.Drawer.CIRCLE);            // Draw Circle
this.canvas.setDrawer(CanvasView.Drawer.ELLIPSE);           // Draw Ellipse (Oval)
this.canvas.setDrawer(CanvasView.Drawer.QUADRATIC_BEZIER);  // Draw Quadratic Bezier

// Getter
CanvasView.Drawer drawer = this.canvas.getDrawer();

Background color

// Setter
this.canvas.setBaseColor(Color.WHITE);

// Getter
int backgroundColor = this.canvas.getBaseColor();

Stroke Style

// Setter
this.canvas.setPaintStyle(Paint.Style.STROKE);
this.canvas.setPaintStyle(Paint.Style.FILL);
this.canvas.setPaintStyle(Paint.Style.FILL_AND_STROKE);

// Getter
Paint.Style strokeStyle = this.canvas.getPaintStyle();

Stroke Color

// Setter
this.canvas.setPaintStrokeColor(Color.RED);

// Getter
int color = this.canvas.getPaintStrokeColor();

Stroke Width

// Setter
this.canvas.setPaintStrokeWidth(2F);

// Getter
float strokeWidth = this.canvas.getPaintStrokeWidth();

Alpha (Opacity)

// Setter
this.canvas.setOpacity(128);  // between 0 and 255

// Getter
int opacity = this.canvas.getOpacity();

Blur

// Setter
this.canvas.setBlur(5F);  // greater than or equal to 0

// Getter
float blur = this.canvas.getBlur();

Line Cap

// Setter
this.canvas.setLineCap(Paint.Cap.BUTT);
this.canvas.setLineCap(Paint.Cap.ROUND);
this.canvas.setLineCap(Paint.Cap.SQUARE);

// Getter
Paint.Cap lineCap = this.canvas.getLineCap();

Draw Text

// Change Mode
this.canvas.setMode(CanvasView.Mode.TEXT);

// Setter
this.canvas.setText("Canvas View");

// Getter
String text = this.canvas.getText();

Font Family / Font Size

// Setter
this.canvas.setFontFamily(Typeface.DEFAULT);
this.canvas.setFontFamily(Typeface.DEFAULT_BOLD);
this.canvas.setFontFamily(Typeface.SANS_SERIF);
this.canvas.setFontFamily(Typeface.SERIF);
this.canvas.setFontFamily(Typeface.MONOSPACE);
this.canvas.setFontSize(24F);  // greater than or equal to 0

// Getter
Typeface fontFamily = this.canvas.getFontFamily();
float fontSize      = this.canvas.getFontSize();

Get Canvas as Bitmap

If application requires to save current canvas as Bitmap, the following methods enable to save.

Bitmap bitmap = this.canvas.getBitmap();

In the case of adjusting size,

Bitmap bitmap = this.canvas.getScaleBitmap(300, 200);  // 300 x 200

In the case of using byte array of bitmap,

// The 1st argument is format.
// The 2nd argument is quality.
byte[] bytes = this.canvas.getBitmapAsByteArray(CompressFormat.PNG, 100);

or,

// Format is PNG. Quality is 100.
byte[] bytes = this.canvas.getBitmapAsByteArray();

In the case of using the specific bitmap,

// ...

byte[] bytes = CanvasView.getBitmapAsByteArray(bitmap, CompressFormat.PNG, 100);

Draw Bitmap to Canvas

From Bitmap,

// ...

this.canvas.drawBitmap(bitmap);

From byte array of bitmap

// ...

this.canvas.drawBitmap(bytes);

mssaravanan/CanvasView