How to remove one color in a image.

[Mohammed Arief]

Hi guy's

I am working on a sprite game in c++ and OpenCV. I have created to images, the backgroundimage (the background image in the game and the spriteman (my character in the game).

How do I remove the colour blue colour around my character?

int main() {

// Loading Images - Loading the Background Image
IplImage* backgroundimage = cvLoadImage("mission11.png"); 
backgroundimage->width;
backgroundimage->height;

// Creating an empty images - Setting the widt and height values as backgroundimage
IplImage* temp = cvCreateImage(cvSize(backgroundimage->width,backgroundimage->height),IPL_DEPTH_8U,3) ;

// Loading Images - Loading the Sprite Image
IplImage* spriteman = cvLoadImage("spriteman.jpg"); //change the file name with your own image
spriteman->width;
spriteman->height;

// The start place of the sprite 
int placeY = 80;
int placeX = 80;

// Creating a variable for the keys ind the game
char presskey;

// The start place of the sprite
bool run = true;

while(run){

	char presskey = cvWaitKey(5);
	
	switch(presskey) {
	case 'w':
	case 38:
		placeY -=10;
		break;
	case 'a':
	case 39:
		placeX -=10;
		break;
	case'd':
	case 40:
		placeX +=10;
		break;
	case's':
	case 41:
		placeY +=10;
		break;
	case 32:
		placeY -=20;
		break;
	case'q':
	case 27:
		run=false;
		break;
	}

	for(int i=0;i<backgroundimage->height*backgroundimage->width*backgroundimage->nChannels;i++){
		temp->imageData[i]=backgroundimage->imageData[i];
	}
	for(int y = 0; y < spriteman->height; y++){
		for(int x = 0; x < spriteman->width; x++){
			for(int z = 0; z < spriteman->nChannels; z++){
				if(((uchar *)(spriteman->imageData + y*spriteman->widthStep))[x*spriteman->nChannels + z] < 260){
					temp->imageData[(y + placeY) * backgroundimage->widthStep + (x+placeX) * backgroundimage->nChannels + z] = spriteman->imageData[y * spriteman->widthStep + x * spriteman->nChannels + z];

				}

			}
		}
	}

	// Display the image temp
	cvShowImage("Metal Slug: Kill Rambo", temp);
}

//create a new window with  
cvNamedWindow("Metal Slug: Kill Rambo", CV_WINDOW_FULLSCREEN);


//Destroying the Window and the Images within
cvDestroyWindow( "Metal Slug: Kill Rambo" );
cvReleaseImage( &backgroundimage );
cvReleaseImage( &temp );
cvReleaseImage( &spriteman );
return 0;

}

[Bala kumar]

Hi,
You are using a png image, so i assume that u r image is 32-bit and ARGB pixel format.

All you have to do is check for each pixel color and if it matches 0xff0000ff than replace it with 0x00000000, so that blue color in the image vil become transparent.

To get more help on web search for color keying algorithm.

Hope this helps.