Android Bitmap Common Several operations: zoom, crop, rotate, offset

Android Bitmap Related actions

Several common operations: zoom, crop, rotate, offset

Many operations require the matrix to support the matrix, which processes the bitmap and calculates the location of each pixel to display the bitmap.
There is a 3x3 matrix in the matrix for image processing:

mscale_x mskew_x  mtrans_xmskew_y  mscale_y mtrans_ympersp_0 mpersp_1 mpersp_2

The specific purpose can be guessed according to the variable name:
Zoom x Offset x Shift x
Offset y scale y shift y
Pivot 0 Pivot 1 Perspective 2

Matrix operations have Set,pre and Post;set to directly set the values in the matrix; the pre is similar to the matrix left multiply; The post is similar to the right multiplication in the matrix.

Once the original bitmap is calculated, a bitmap is regenerated

Code snippet:

    /*** Stretch according to a given width and height *@paramOriginal Origin *@paramNewwidth The width of the new chart *@paramnewheight height of the new chart *@returnNew Bitmap*/    PrivateBitmap Scalebitmap (Bitmap origin,intNewwidth,intnewheight) {        if(Origin = =NULL) {            return NULL; }        intHeight =origin.getheight (); intwidth =origin.getwidth (); floatScaleWidth = ((float) newwidth)/width; floatScaleHeight = ((float) newheight)/height; Matrix Matrix=NewMatrix (); Matrix.postscale (ScaleWidth, scaleheight);//use post-multiplyBitmap NEWBM = Bitmap.createbitmap (origin, 0, 0, width, height, matrix,false); if(!origin.isrecycled ())        {origin.recycle (); }        returnNEWBM; }    /*** Proportionally scaled picture * *@paramOriginal Origin *@paramratio ratio *@returnthe new bitmap*/    PrivateBitmap Scalebitmap (Bitmap origin,floatratio) {        if(Origin = =NULL) {            return NULL; }        intwidth =origin.getwidth (); intHeight =origin.getheight (); Matrix Matrix=NewMatrix ();        Matrix.prescale (ratio, ratio); Bitmap NEWBM= Bitmap.createbitmap (origin, 0, 0, width, height, matrix,false); if(Newbm.equals (Origin)) {returnNEWBM;        } origin.recycle (); returnNEWBM; }    /*** Crop * *@paramBitmap Original *@returnCropped image*/    PrivateBitmap Cropbitmap (Bitmap Bitmap) {intW = bitmap.getwidth ();//get the picture wide and high        inth =bitmap.getheight (); intCropwidth = w >= h? H:w;//edge length of square area taken after croppingCropwidth/= 2; intCropheight = (int) (cropwidth/1.2); returnBitmap.createbitmap (Bitmap, W/3, 0, Cropwidth, Cropheight,NULL,false); }    /*** Select Transform * *@paramOriginal Origin *@paramAlpha Rotation angle, can be negative *@returnthe rotated picture*/    PrivateBitmap Rotatebitmap (Bitmap origin,floatAlpha) {        if(Origin = =NULL) {            return NULL; }        intwidth =origin.getwidth (); intHeight =origin.getheight (); Matrix Matrix=NewMatrix ();        Matrix.setrotate (Alpha); //rotate around in situBitmap NEWBM = Bitmap.createbitmap (origin, 0, 0, width, height, matrix,false); if(Newbm.equals (Origin)) {returnNEWBM;        } origin.recycle (); returnNEWBM; }    /*** Offset Effect *@paramOriginal Origin *@returnbitmap after the offset*/    PrivateBitmap Skewbitmap (Bitmap origin) {if(Origin = =NULL) {            return NULL; }        intwidth =origin.getwidth (); intHeight =origin.getheight (); Matrix Matrix=NewMatrix (); Matrix.postskew (-0.6f, -0.3f); Bitmap NEWBM= Bitmap.createbitmap (origin, 0, 0, width, height, matrix,false); if(Newbm.equals (Origin)) {returnNEWBM;        } origin.recycle (); returnNEWBM; }

The operation definition of the button:

@Override Public voidOnClick (View v) {Bitmap ORIGINBM=Bitmapfactory.decoderesource (Getresources (), r.drawable.littleboygreen_x128); Switch(V.getid ()) { CaseR.ID.BTN1: {//scale by SizeEffecttextview.settext (R.string.scale); Bitmap NBM= Scalebitmap (ORIGINBM, 100, 72);                Effectview.setimagebitmap (NBM);  Break; }             CaseR.ID.BTN2: {//Scaled proportionally , each click will be differentEffecttextview.settext (R.string.scale_ratio); if(ratio < 3) {ratio+ = 0.05f; } Else{ratio= 0.1f; } Bitmap NBM=Scalebitmap (ORIGINBM, ratio);                Effectview.setimagebitmap (NBM);  Break; }             CaseR.ID.BTN3: {//croppingEffecttextview.settext ("Cut the head"); Bitmap Cropbitmap=Cropbitmap (ORIGINBM);                Effectview.setimagebitmap (CROPBITMAP);  Break; }             CaseR.ID.BTN4: {//clockwise rotation effect; update rotation angle per click                if(Alpha < 345) {Alpha+ = 15; } Else{Alpha= 0; } effecttextview.settext (Rotation); Bitmap Rotatebitmap=Rotatebitmap (ORIGINBM, Alpha);                Effectview.setimagebitmap (ROTATEBITMAP);  Break; }             CaseR.id.btn5: {//counter-clockwise rotation effect; update rotation angle per click                if(Beta > 15) {Beta-= 15; } Else{Beta= 360; } effecttextview.settext (Rotation); Bitmap Rotatebitmap=rotatebitmap (ORIGINBM, beta);                Effectview.setimagebitmap (ROTATEBITMAP);  Break; }             CaseR.ID.BTN6: {//Offset effect; offset in methodBitmap SKEWBM =Skewbitmap (ORIGINBM);                Effectview.setimagebitmap (SKEWBM);  Break; }        }    }

Problems encountered

New Matrix (); Matrix.prescale (ratio, ratio); // when Ratio=1, the following NEWBM will be equivalent to Origin false ); if (! origin.isrecycled ()) {origin.recycle ();}

Log as follows, when Ratio=1, the new bitmap and the old bitmap the same address

11-27 05:27:16.086 16723-16723/? D/rust:originbitmap = [email protected]
11-27 05:27:16.086 16723-16723/? D/rust:newbitmap = [email protected]

Android Bitmap Common Several operations: zoom, crop, rotate, offset