Android缩放图片的两种方法

缩放图片有两种手段：

1.缩放图片所在的ImageView.

2.缩放ImageView依附的Bitmap.

这两种方式共同套路就是

1.确定Bitmap的宽高，进而求得宽高比例.

2.ImageView根据Bitmap的宽高比确定自己的宽高.

• 缩放ImageView

Bitmap originalBitmap = Bitmap.decodeResouce(getResource(), R.drawable.demo_bitmap);

float bitmapWidth = originalBitmap.getWidth();

float bitmapHeight = originlBitmap.getHeight();

float bitmapRatio = bitmapWidth / bitmapHeight;

ImageView imgView = findViewById(R.id.img);

ViewGroup.LayoutParams params= imgView.getLayoutParams();

// 默认我们就设置图片和屏幕一样宽

params.width = Utils.getScreenSize();

params.height = params.width / bitmapRatio;

imgView.setLayoutParams(params);

// 算出图片的缩放比，以长度为基准

float scale = params.width / bitmap.width;

Matrix matrix = new Matrix();

matrix.postScale(scale, scale);

imgView.setScaleType(ScaleType.MATRIX);

imgView.setMatrix(matrix);

• 缩放Bitmap

Bitmap originalBitmap = Bitmap originalBitmap = Bitmap.decodeResouce(getResource(), R.drawable.demo_bitmap);

float bitmapRatio = bitmapWidth / bitmapHeight;

ImageView imgView = findViewById(R.id.img);

ViewGroup.LayoutParams params= imgView.getLayoutParams();

// 同样要确定ImageView的宽高

params.width = Utils.getScreenSize();

params.height = params.width / bitmapRatio;

imgView.setLayoutParams(params);

// 计算Bitmap的缩放比例

float bitmapScale = params.width / bitmapWidth;

Matrix matrix = new Matrix();

matrix.postScale(bitmapScale, bitmapScale);

// 设置缩放后的Bitmap

Bitmap scaleBitmap = Bitmap.create(originalBitmap,0,0,originalBitmap.getWidth(), originalBitmap.getHeight(),matrix, true);

imgView.setBitmap(scaleBitmap);