[置顶] 很实用的android压缩图片的算法

这些天一直为android程序如何压缩图片烦恼，上网找了很多资料，整理了一下，经过测试，都是可用的，

/**
	 * 压缩图片
	 * @param bitmap 源图片
	 * @param width 想要的宽度
	 * @param height 想要的高度
	 * @param isAdjust 是否自动调整尺寸, true图片就不会拉伸，false严格按照你的尺寸压缩
	 * @return Bitmap
	 */
	public Bitmap reduce(Bitmap bitmap, int width, int height, boolean isAdjust) {
		// 如果想要的宽度和高度都比源图片小，就不压缩了，直接返回原图
		if (bitmap.getWidth() < width && bitmap.getHeight() < height) {return bitmap;}
		// 根据想要的尺寸精确计算压缩比例, 方法详解：public BigDecimal divide(BigDecimal divisor, int scale, int roundingMode);
		// scale表示要保留的小数位, roundingMode表示如何处理多余的小数位，BigDecimal.ROUND_DOWN表示自动舍弃
		float sx = new BigDecimal(width).divide(new BigDecimal(bitmap.getWidth()), 4, BigDecimal.ROUND_DOWN).floatValue();
		float sy = new BigDecimal(height).divide(new BigDecimal(bitmap.getHeight()), 4, BigDecimal.ROUND_DOWN).floatValue();
		if (isAdjust) {// 如果想自动调整比例，不至于图片会拉伸
			sx = (sx < sy ? sx : sy);sy = sx;// 哪个比例小一点，就用哪个比例
		}
		Matrix matrix = new Matrix();
		matrix.postScale(sx, sy);// 调用api中的方法进行压缩，就大功告成了
		return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
	}

旋转图片：

/**
	 * 旋转图片
	 * @param bitmap 源图片
	 * @param angle 旋转角度(90为顺时针旋转,-90为逆时针旋转)
	 * @return Bitmap
	 */
	public Bitmap rotate(Bitmap bitmap, float angle) {
		Matrix matrix = new Matrix();  
		matrix.postRotate(angle);
		return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
	}

放大或缩小图片：

/**
	 * 放大或缩小图片
	 * @param bitmap 源图片
	 * @param ratio 放大或缩小的倍数，大于1表示放大，小于1表示缩小
	 * @return Bitmap
	 */
	public Bitmap zoom(Bitmap bitmap, float ratio) {
		if (ratio < 0f) {return bitmap;}
		Matrix matrix = new Matrix();
		matrix.postScale(ratio, ratio);
		return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
	}

在图片上印字：

/**
	 * 在图片上印字
	 * @param bitmap 源图片
	 * @param text 印上去的字
	 * @param param 字体参数分别为：颜色,大小,是否加粗,起点x,起点y; 比如：{color : 0xFF000000, size : 30, bold : true, x : 20, y : 20}
	 * @return Bitmap
	 */
	public Bitmap printWord(Bitmap bitmap, String text, Map<String, Object> param) {
		if (ToolUtil.get().isBlank(text) || null == param) {return bitmap;}
		Bitmap newBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
		Canvas canvas = new Canvas(newBitmap);
		canvas.drawBitmap(bitmap, 0, 0, null);canvas.save(Canvas.ALL_SAVE_FLAG);canvas.restore();
		Paint paint = new Paint();
		paint.setColor(null != param.get("color") ? (Integer) param.get("color") : Color.BLACK);
		paint.setTextSize(null != param.get("size") ? (Integer) param.get("size") : 20);
		paint.setFakeBoldText(null != param.get("bold") ? (Boolean) param.get("bold") : false);
		canvas.drawText(text, null != param.get("x") ? (Integer) param.get("x") : 0, null != param.get("y") ? (Integer) param.get("y") : 0, paint);
		canvas.save(Canvas.ALL_SAVE_FLAG);canvas.restore();
		return newBitmap;
	}

创建logo(给图片加水印), ：

/**
	 * 创建logo(给图片加水印), 
	 * @param bitmaps 原图片和水印图片
	 * @param left 左边起点坐标
	 * @param top 顶部起点坐标t
	 * @return Bitmap
	 */
	public Bitmap createLogo(Bitmap[] bitmaps, int left, int top) {
		Bitmap newBitmap = Bitmap.createBitmap(bitmaps[0].getWidth(), bitmaps[0].getHeight(), Config.ARGB_8888);
		Canvas canvas = new Canvas(newBitmap);
		for (int i = 0; i < bitmaps.length; i++) {
			if (i == 0) {
				canvas.drawBitmap(bitmaps[0], 0, 0, null);
			} else {
				canvas.drawBitmap(bitmaps[i], left, top, null);
			}
			canvas.save(Canvas.ALL_SAVE_FLAG);canvas.restore();
		}
		return newBitmap;
	}

产生一个4位随机数字的图片验证码：

private int width = 140, height = 40, codeLen = 4;
	private String checkCode = "";
	private Random random = new Random();
	
	/**
	 * 产生一个4位随机数字的图片验证码
	 * @return Bitmap
	 */
	public Bitmap createCode() {
		checkCode = "";
		String[] chars = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
		for (int i = 0; i < codeLen; i++) {checkCode += chars[random.nextInt(chars.length)];}
		Bitmap bitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888);
		Canvas canvas = new Canvas(bitmap);canvas.drawColor(Color.WHITE);
		Paint paint = new Paint();paint.setTextSize(30);paint.setColor(Color.BLUE);
		for (int i = 0; i < checkCode.length(); i++) {
			paint.setColor(randomColor(1));paint.setFakeBoldText(random.nextBoolean());
			float skewX = random.nextInt(11) / 10;
			paint.setTextSkewX(random.nextBoolean() ? skewX : -skewX);
			int x = width / codeLen * i + random.nextInt(10);
			canvas.drawText(String.valueOf(checkCode.charAt(i)), x, 28, paint);
		}
		for (int i = 0; i < 3; i++) {drawLine(canvas, paint);}
		for (int i = 0; i < 255; i++) {drawPoints(canvas, paint);}
		canvas.save(Canvas.ALL_SAVE_FLAG);canvas.restore();
		return bitmap;
	}
	
	/**
	 * 获得一个随机的颜色
	 * @param rate
	 * @return 
	 */
	public int randomColor(int rate) {
		int red = random.nextInt(256) / rate, green = random.nextInt(256) / rate, blue = random.nextInt(256) / rate;
		return Color.rgb(red, green, blue);
	}

	/**
	 * 画随机线条
	 * @param canvas
	 * @param paint
	 */
	public void drawLine(Canvas canvas, Paint paint) {
		int startX = random.nextInt(width), startY = random.nextInt(height);
		int stopX = random.nextInt(width), stopY = random.nextInt(height);
		paint.setStrokeWidth(1);paint.setColor(randomColor(1));
		canvas.drawLine(startX, startY, stopX, stopY, paint);
	}

	/**
	 * 画随机干扰点
	 * @param canvas
	 * @param paint
	 */
	public void drawPoints(Canvas canvas, Paint paint) {
		int stopX = random.nextInt(width), stopY = random.nextInt(height);
		paint.setStrokeWidth(1);
		paint.setColor(randomColor(1));
		canvas.drawPoint(stopX, stopY, paint);
	}
	
	/**
	 * 返回真实验证码字符串
	 * @return String
	 */
	public String getCheckCode() {
		return checkCode;
	}