c# - Need help for merging one image with another image -

suppose programmatically comparing between 2 images. after extracting difference between 2 images suppose store difference in bitmap variable called bmp3

i got code site show how merge difference first image.

suppose have 2 bitmap variables called bmp1 & bmp2. extract programmatically difference between 2 variable called bmp1 & bmp2 , store in bmp3 variable.

now want merge difference bmp1 variable @ same position. got code site , works fine have confusion few line of code.

here code:

bitmap bcomb = new bitmap(bmp3.width, bmp3.height);  using (graphics g = graphics.fromimage(bcomb)) {     g.drawimage(this.picturebox1.image, 0, 0, bcomb.width, bcomb.height);     g.drawimage(bmp3, 0, 0, bcomb.width, bcomb.height); }  this.picturebox4.image = bcomb; 

the meaning of line is

bitmap bcomb = new bitmap(bmp3.width, bmp3.height); 

bcom new variable have same size of bmp3....... right ?

the meaning of line g.drawimage(this.picturebox1.image, 0, 0, bcomb.width, bcomb.height); ?

we writing picbox1 content bcom variable 0,0 coordinate....am right ?

again writing bmp3 content bcom variable 0,0 coordinate again....am right ?

this last line making confusion me. why write bmp3 variable content bcom variable 0,0 coordinate again....am right ?

if write both 0,0 coordinate again bcom variable pic should on lap on each other output coming right. how being possible.

i need understand couple of line. please discuss line in detail , why 0,0 coordinate used. please me understand code. thanks

1. bcomb new variable have same size of bmp3 ....... right ?

yes , it's bitmap size of bmp3 we'll use draw other stuff on contains empty pixels , nothing more !

2.

using (graphics g = graphics.fromimage(bcomb)) 

this line gives ability draw whatever need on bcomb can bitmap or rectangle or !

3.

g.drawimage(this.picturebox1.image, 0, 0, bcomb.width, bcomb.height); 

here draws this.picturebox1.image bitmap (bcomb) point (0,0) (bcomb.width,bcomb.height) contain whole bitmap indeed

4.

g.drawimage(bmp3, 0, 0, bcomb.width, bcomb.height); 

bmp3 being drawn bcomb here again point (0,0) (bcomb.width,bcomb.height)

the bitmaps being drawn on each other same point , same size , point if contain transparent pixels result combination of bitmaps , otherwise see bmp3 drawn later , no clue of first image , , use (0,0) because it's beginning point of our bitmap , use other point draw our stuff in way leave pixels behind why ? :)

• update : it's totally possible draw images on each other , you're right if have transparent pixels result marge , mentioned if last bitmap not contain transparent pixels picture we're gonna see last 1 , won't able see previous bitmaps because pixels over-written last bitmap feel free to use png semi-transparent images , drawing them on top of each other , see result , , i'm afraid , don't know built-in gdi+ function image comparison can getpixel() function in gdi+ , comparing each pixel 1 bitmap or may use unsafe code , access memory directly totally depends on if want clean , easy way go getpixel() ! may take @ intel's open-cv library image processing , hope helps