Scale Types

我们可以利用adjustViewBounds参数来保留此宽高比。 但是，我们必须允许高度和/或宽度可调（即通过使用maxWidth并使用wrap_content）。 否则，不能重新调整尺寸以满足所需的宽高比。

image-scaletype.png

图像缩放以适合父视图的宽度，并且应该按比例调整高度。

public class ResizableImageView extends ImageView {

    public ResizableImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override 
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
         Drawable d = getDrawable();

         if(d!=null){
                 // ceil not round - avoid thin vertical gaps along the left/right edges
                 int width = MeasureSpec.getSize(widthMeasureSpec);
                 int height = (int) Math.ceil((float) width * (float) d.getIntrinsicHeight() / (float) d.getIntrinsicWidth());
                 setMeasuredDimension(width, height);
         }else{
                 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
         }
    }

}

支持多种密度的图像

image-densities.png

Final Android Resizer

这个程序允许我们选择一个高密度图像，该工具将自动生成相应的较小尺寸的图像：

image-resizer.png

Scaling a Bitmap——[createScaledBitmap]

不保留宽高比(http://developer.android.com/reference/android/graphics/Bitmap.html#createScaledBitmap(android.graphics.Bitmap,%20int,%20int,%20boolean))

// Load a bitmap from the drawable folder
Bitmap bMap = BitmapFactory.decodeResource(getResources(), R.drawable.my_image);
// Resize the bitmap to 150x100 (width x height)
Bitmap bMapScaled = Bitmap.createScaledBitmap(bMap, 150, 100, true);
// Loads the resized Bitmap into an ImageView
ImageView image = (ImageView) findViewById(R.id.test_image);
image.setImageBitmap(bMapScaled);

保留宽高比

public class BitmapScaler
{
    // Scale and maintain aspect ratio given a desired width
    // BitmapScaler.scaleToFitWidth(bitmap, 100);
    public static Bitmap scaleToFitWidth(Bitmap b, int width)
    {
        float factor = width / (float) b.getWidth();
        return Bitmap.createScaledBitmap(b, width, (int) (b.getHeight() * factor), true);
    }


    // Scale and maintain aspect ratio given a desired height
    // BitmapScaler.scaleToFitHeight(bitmap, 100);
    public static Bitmap scaleToFitHeight(Bitmap b, int height)
    {
        float factor = height / (float) b.getHeight();
        return Bitmap.createScaledBitmap(b, (int) (b.getWidth() * factor), height, true);
    }

    // ...
}

依据屏幕宽高缩放bitmap

public Bitmap scaleToActualAspectRatio(Bitmap bitmap) {
 if (bitmap != null) {
 boolean flag = true;
 
int deviceWidth = getWindowManager().getDefaultDisplay()
 .getWidth();
 int deviceHeight = getWindowManager().getDefaultDisplay()
 .getHeight();
 
int bitmapHeight = bitmap.getHeight(); // 563
 int bitmapWidth = bitmap.getWidth(); // 900
 
// aSCPECT rATIO IS Always WIDTH x HEIGHT rEMEMMBER 1024 x 768
 
if (bitmapWidth > deviceWidth) {
 flag = false;
 
// scale According to WIDTH
 int scaledWidth = deviceWidth;
 int scaledHeight = (scaledWidth * bitmapHeight) / bitmapWidth;
 
try {
 if (scaledHeight > deviceHeight)
 scaledHeight = deviceHeight;
 
bitmap = Bitmap.createScaledBitmap(bitmap, scaledWidth,
 scaledHeight, true);
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
 
if (flag) {
 if (bitmapHeight > deviceHeight) {
 // scale According to HEIGHT
 int scaledHeight = deviceHeight;
 int scaledWidth = (scaledHeight * bitmapWidth)
 / bitmapHeight;
 
try {
 if (scaledWidth > deviceWidth)
 scaledWidth = deviceWidth;
 
bitmap = Bitmap.createScaledBitmap(bitmap, scaledWidth,
 scaledHeight, true);
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
 }
 }
 return bitmap;
 }

注意：对图像进行任何类型的缩放都会导致EXIF元数据丢失，包括相机，旋转，所拍照片的日期/时间等信息。 虽然在复制映像后传输此数据有一些解决方法，但是存在当前的限制。 如果您需要此信息或希望将其上传到某个网站，您应该发送原始文件。

SVG

ImageView中使用SVG

// Parse an SVG resource from the "raw" resource folder
SVG svg = SVGParser.getSVGFromResource(getResources(), R.raw.android);
// Fix issue with renderer on certain devices
myImageView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
// Get a drawable from the parsed SVG and set it as the drawable for the ImageView
myImageView.setImageDrawable(svg.createPictureDrawable());

Canvas中使用SVG

// Parse the SVG file from the resource 
SVG svg =SVGParser.getSVGFromResource(getResources(), R.raw.android); 
// Get the picture 
Picture picture = svg.getPicture(); 
// Draw picture in canvas 
// Note: use transforms such as translate, scale and rotate to position the picture correctly
canvas.drawPicture(picture); 
// ...

Bounds和Limits

// Parse SVG 
SVG svg = SVGParser.getSVGFromResource(getResources(), R.raw.android); 
// Get the artist-specified bounds (will be null if not specified) 
RectF bounds = svg.getBounds(); 
// Get the parser-estimated bounds (could also be null, for example if it is a blank SVG) 
RectF limits = svg.getLimits();