android压缩图片的算法，加水印,图片验证码

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，

[java] view
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/**

* 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：

[java] view
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/**

* 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：

[java] view
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/**

* 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：

[java] view
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/**

* 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), ：

[java] view
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/**

* 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：

[java] view
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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;

}