ppu-ocv/canvas-regions.js

A type-safe, modular, chainable image processing library built on top of OpenCV.js with a fluent API leveraging pipeline processing.

export function detectRegions(data,width,height,options={}){const{foreground="light",thresh=127,minArea=1,maxArea=1/0,padding,scale=1}=options;let visited=new Uint8Array(width*height);let regions=[];let neighbours=[[-1,-1],[0,-1],[1,-1],[-1,0],[1,0],[-1,1],[0,1],[1,1]];let isForeground=(pixelIdx)=>{let r=data[pixelIdx]??0;return foreground==="light"?r>thresh:r<=thresh};for(let startY=0;startY<height;startY++){for(let startX=0;startX<width;startX++){let startFlat=startY*width+startX;if(visited[startFlat])continue;visited[startFlat]=1;if(!isForeground(startFlat*4))continue;let stack=[startFlat];let minX=startX,maxX=startX;let minY=startY,maxY=startY;let area=0;while(stack.length>0){let flat=stack.pop();if(flat===undefined)break;area++;let x=flat%width;let y=(flat-x)/width;if(x<minX)minX=x;else if(x>maxX)maxX=x;if(y<minY)minY=y;else if(y>maxY)maxY=y;for(const[dx,dy]of neighbours){let nx=x+dx;let ny=y+dy;if(nx<0||nx>=width||ny<0||ny>=height)continue;let nFlat=ny*width+nx;if(visited[nFlat])continue;visited[nFlat]=1;if(isForeground(nFlat*4))stack.push(nFlat)}}if(area>=minArea&&area<=maxArea){let x0=minX;let y0=minY;let x1=maxX+1;let y1=maxY+1;if(padding){let bboxH=y1-y0;let vPad=Math.round(bboxH*(padding.vertical??0));let hPad=Math.round(bboxH*(padding.horizontal??0));x0=Math.max(0,x0-hPad);y0=Math.max(0,y0-vPad);x1=Math.min(width,x1+hPad);y1=Math.min(height,y1+vPad)}if(scale!==1){x0=Math.max(0,Math.round(x0*scale));y0=Math.max(0,Math.round(y0*scale));x1=Math.round(x1*scale);y1=Math.round(y1*scale)}regions.push({bbox:{x0,y0,x1,y1},area})}}}return regions}