1 加载图片到内存
（1）.数码相机照片特别是大于3m以上的，内存吃不消，会报OutOfMemoryError,若是想只显示原图片的1/8,可以通过BitmapFactory.Options来实现，具体代码如下：
| BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options(); bmpFactoryOptions.inSampleSize = 8; Bitmap bmp = BitmapFactory.decodeFile(imageFilePath, bmpFactoryOptions); imv.setImageBitmap(bmp); 如果图片太大，会出现的以下的问题：
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| 2 根据当前屏幕分辨率的大小，加载图片 Display currentDisplay = getWindowManager().getDefaultDisplay(); int dw = currentDisplay.getWidth(); int dh = currentDisplay.getHeight();
BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options(); bmpFactoryOptions.inJustDecodeBounds = true; Bitmap bmp = BitmapFactory.decodeFile(imageFilePath, bmpFactoryOptions); //通过下面的代码计算缩放比，那个方向的缩放比大，就按照这把方向的缩放比来缩放。 int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)dh); int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)dw); Log.v("HEIGHTRATIO",""+heightRatio); Log.v("WIDTHRATIO",""+widthRatio);
//判断是否要进行缩放 if (heightRatio > 1 && widthRatio > 1) { if (heightRatio > widthRatio) { //高度变化大,按高度缩放 bmpFactoryOptions.inSampleSize = heightRatio; } else { // 宽度变化大,按宽度缩放 bmpFactoryOptions.inSampleSize = widthRatio; } } bmpFactoryOptions.inJustDecodeBounds = false; bmp = BitmapFactory.decodeFile(imageFilePath, bmpFactoryOptions); |
| 3 获取Exif图片信息 //从文件获取exif信息 ExifInterface ei = new ExifInterface(imageFilePath); String imageDescription = ei.getAttribute("ImageDescription"); if (imageDescription != null) { Log.v("EXIF", imageDescription); } //把exif信息写到文件: ExifInterface ei = new ExifInterface(imageFilePath); ei.setAttribute("ImageDescription","Something New"); |
| 4 从gallery获取一个图片 Intent intent = new Intent(Intent.ACTION_PICK); intent.setType(“image/*”); intent.getData() 获取image的uri Bitmap bmp = BitmapFactory.decodeStream(getContentResolver(). openInputStream(imageFileUri), null, bmpFactoryOptions); |
| 5 创建bitmap拷贝 Bitmap bmp = BitmapFactory.decodeStream(getContentResolver(). openInputStream(imageFileUri), null, bmpFactoryOptions); Bitmap alteredBitmap = Bitmap.createBitmap(bmp.getWidth(),bmp.getHeight(), bmp.getConfig()); Canvas canvas = new Canvas(alteredBitmap); Paint paint = new Paint(); canvas.drawBitmap(bmp, 0, 0, paint); |
| 6 图形缩放 Matrix matrix = new Matrix(); matrix.setValues(new float[] { 1, 0, 0, 0, 1, 0, 0, 0, 1 }); x = 1x + 0y + 0z y = 0x + 1y + 0z z = 0x + 0y + 1z 通过canvas.drawBitmap(bmp, matrix, paint);创建bitmap 1.水平缩放0.5 2.垂直拉扯2倍 matrix.setScale(1.5f,1);//水平点放大到1.5f,垂直1 |
| 7 图形旋转 Matrix matrix = new Matrix(); matrix.setRotate(15); canvas.drawBitmap(bmp, matrix, paint); 消除锯齿 paint.setAntiAlias(true); 指定圆心的旋转 matrix.setRotate(15,bmp.getWidth()/2,bmp.getHeight()/2); Matrix matrix = new Matrix(); matrix.setRotate(15,bmp.getWidth()/2,bmp.getHeight()/2); alteredBitmap = Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(), bmp.getHeight(), matrix, false); alteredImageView.setImageBitmap(alteredBitmap); |
| 8 图像平移： setTranslate(1.5f,-10); 9 镜子效果： matrix.setScale(-1, 1); matrix.postTranslate(bmp.getWidth(),0); 10 倒影效果： matrix.setScale(1, -1); matrix.postTranslate(0, bmp.getHeight()); |
| 11 图像颜色处理： 颜色矩阵 ColorMatrix cm = new ColorMatrix(); paint.setColorFilter(new ColorMatrixColorFilter(cm)); 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 New Red Value = 1*128 + 0*128 + 0*128 + 0*0 + 0 New Blue Value = 0*128 + 1*128 + 0*128 + 0*0 + 0 New Green Value = 0*128 + 0*128 + 1*128 + 0*0 + 0 New Alpha Value = 0*128 + 0*128 + 0*128 + 1*0 + 0 ColorMatrix cm = new ColorMatrix(); cm.set(new float[] { 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0 }); paint.setColorFilter(new ColorMatrixColorFilter(cm)); |
| 12 变换图像的亮度 ColorMatrix cm = new ColorMatrix(); float contrast = 2; cm.set(new float[] { contrast, 0, 0, 0, 0, 0, contrast, 0, 0, 0, 0, 0, contrast, 0, 0, 0, 0, 0, 1, 0 }); paint.setColorFilter(new ColorMatrixColorFilter(cm)); |
| 12 变换图像的亮度 ColorMatrix cm = new ColorMatrix(); float contrast = 2; cm.set(new float[] { contrast, 0, 0, 0, 0, 0, contrast, 0, 0, 0, 0, 0, contrast, 0, 0, 0, 0, 0, 1, 0 }); paint.setColorFilter(new ColorMatrixColorFilter(cm)); |
| 13 更改图片的饱和度： ColorMatrix cm = new ColorMatrix(); cm.setSaturation(.5f); paint.setColorFilter(new ColorMatrixColorFilter(cm)); |
| 14 图像合成: Bitmap drawingBitmap = Bitmap.createBitmap(bmp1.getWidth(),bmp1.getHeight(), bmp1.getConfig()); canvas = new Canvas(drawingBitmap); paint = new Paint(); canvas.drawBitmap(bmp1, 0, 0, paint); paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.MULTIPLY)); canvas.drawBitmap(bmp2, 0, 0, paint); |
| 15 按指定path上绘制文字 Paint paint = new Paint(); paint.setColor(Color.GREEN); paint.setTextSize(20); paint.setTypeface(Typeface.DEFAULT); Path p = new Path(); p.moveTo(20, 20); p.lineTo(100, 150); p.lineTo(200, 220); canvas.drawTextOnPath("Hello this is text on a path", p, 0, 0, paint); |
| 16 人脸识别 FaceDetector detector = new FaceDetector(faceBitmap.getWidth(), faceBitmap.getHeight(), 3); // 创建识别器 mNumFaces = detector.findFaces(faceBitmap, mFaces); // 识别 if (mNumFaces > 0) { for (int i = 0; i < mNumFaces; i++) { handleFace(mFaces[i]); //调用函数对人脸画面进行处理 } } |
| 关于人脸识别部分（网站地址是）： http://www.faceplusplus.com/ |
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1 场景：一张图片很大，放到手机上时需要对图片资源进行压缩以及缩放，编写如下界面的案例：
2 操作：当点击加载图片到内存时，图片从自己的手机sd卡中取到并显示。
3 ADT开发时，手机连接上电脑后，在Android开发工具中的”FileExplorer”中的文件位置如下：
4 下面开始编写代码，项目结构如下：
5 编写activity_main.xml，代码如下：
| <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity" >
<Button android:onClick="click" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="加载图片到内存" />
<ImageView android:id="@+id/iv" android:layout_width="fill_parent" android:layout_height="fill_parent" />
</LinearLayout> |
6 编写MainActivity，代码如下：
| package com.itheima.loadimg;
import android.app.Activity; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.BitmapFactory.Options; import android.os.Bundle; import android.view.View; import android.view.WindowManager; |