adding image rotation to PixelForge gif tool (#5309)

wled00/data/pixelforge/pixelforge.htm

@@ -25,13 +25,13 @@ h3 {
 }
 /* shimmer text animation */
 .title .sh {
-  background: linear-gradient(90deg,
-    #7b47db 0%, #ff6b6b 20%, #feca57 40%, #48dbfb 60%, #7b47db 100%);
-  background-size: 200% 100%;
-  -webkit-background-clip: text;
-  -webkit-text-fill-color: transparent;
-  animation: shimmer 4s ease-in-out 5;
-  font-size: 36px;
+	background: linear-gradient(90deg,
+		#7b47db 0%, #ff6b6b 20%, #feca57 40%, #48dbfb 60%, #7b47db 100%);
+	background-size: 200% 100%;
+	-webkit-background-clip: text;
+	-webkit-text-fill-color: transparent;
+	animation: shimmer 4s ease-in-out 5;
+	font-size: 36px;
 }
 @keyframes shimmer { 50% { background-position: 600% 0; } }
 
@@ -278,11 +278,15 @@ button, .btn {
 
 			<div class="cw">
 				<div style="width:100%">
+					<div class="slc">
+						<label>Rotation:  <span id="rotVal">0</span>° <input type="checkbox" id="snap">snap</label>
+						<input type="range" id="rotSl" min="0" max="359" value="0" class="sl">
+					</div>
 					<div class="slc">
 						<label>Zoom: </label>
 						<input type="range" id="zoom" min="0" max="100" value="0" class="sl">
 					</div>
-					<canvas id="cv" width="500" height="400"></canvas>
+					<canvas id="cv" width="500" height="500"></canvas>
 				</div>
 
 				<small>Preview at target resolution</small>
@@ -430,9 +434,11 @@ const txtFX = 122;   // scrolling text effect number
 /* canvases */
 const cv=gId('cv'),cx=cv.getContext('2d',{willReadFrequently:true});
 const pv=gId('pv'),pvx=pv.getContext('2d',{willReadFrequently:true});
+const rv = cE('canvas'), rvc = rv.getContext('2d',{willReadFrequently:true}); // off screen canvas for drawing resized & rotated image
+rv.width = cv.width; rv.height = cv.height;
 
 /* globals */
-let wu='',sI=null,sF=null,cI=null,bS=1,iS=1,pX=0,pY=0;
+let wu='',sI=null,sF=null,cI=null,bS=1,iS=1,pX=0,pY=0,rot=0;
 let cr={x:50,y:50,w:200,h:150},drag=false,dH=null,oX=0,oY=0;
 let pan=false,psX=0,psY=0,poX=0,poY=0;
 let iL=[]; // image list
@@ -774,6 +780,16 @@ gId('zoom').oninput=()=>{
 	crClamp(); crDraw();
 };
 
+/* rotation */
+function rotUpd(v){
+	if(gId('snap').checked) v = Math.round(v/15)*15 % 360; // snap to multiples of 15°
+	rot = v;
+	gId('rotVal').textContent = v;
+	if(cI) crDraw();
+}
+gId('rotSl').oninput = ()=> rotUpd(+gId('rotSl').value);
+
+
 /* color change */
 gId('bg').oninput=crDraw;
 
@@ -882,12 +898,25 @@ cv.ontouchcancel=e=>{e.preventDefault();actEnd();};
 
 /* draw + preview */
 function crDraw(){
+	if(!cI) return;
+
+	// render rotated image to offscreen
+	rvc.clearRect(0,0,rv.width,rv.height);
+	rvc.fillStyle = gId('bg').value;
+	rvc.fillRect(0,0,rv.width,rv.height);
+	rvc.imageSmoothingEnabled = false;
+	rvc.save();
+	const dw = cI.width * iS, dh = cI.height * iS;
+	rvc.translate(pX + dw/2, pY + dh/2);
+	rvc.rotate(rot * Math.PI / 180);
+	rvc.drawImage(cI, -dw/2, -dh/2, dw, dh);
+	rvc.restore();
+
+	// copy offscreen to visible
 	cx.clearRect(0,0,cv.width,cv.height);
-	if(!cI)return;
-	cx.fillStyle=gId('bg').value; cx.fillRect(0,0,cv.width,cv.height);
-	cx.imageSmoothingEnabled=false;
-	cx.drawImage(cI,0,0,cI.width,cI.height,pX,pY,cI.width*iS,cI.height*iS);
-	/* crop frame */
+	cx.drawImage(rv, 0, 0);
+
+	// overlay crop frame (only on visible)
 	cx.lineWidth=3; cx.setLineDash([6,4]); cx.shadowColor="#000"; cx.shadowBlur=2;
 	cx.strokeStyle="#FFF"; cx.beginPath(); cx.roundRect(cr.x,cr.y,cr.w,cr.h,6); cx.stroke();
 	cx.shadowColor="#000F";
@@ -913,7 +942,8 @@ function prevUpd(){
 	const tcx = tc.getContext('2d');
 	tcx.fillStyle=gId('bg').value;
 	tcx.fillRect(0,0,w,h); // fill background (for transparent images)
-	tcx.drawImage(cI,(cr.x-pX)/iS,(cr.y-pY)/iS,cr.w/iS,cr.h/iS,0,0,w,h);
+	tcx.imageSmoothingEnabled = false;
+	tcx.drawImage(rv, cr.x, cr.y, cr.w, cr.h, 0, 0, w, h); // sample cropped area from off screen canvas
 	blackTh(tcx);
 	// scale/stretch to preview canvas, limit to 256px in largest dimension but keep aspect ratio
 	const ratio = h/w;
@@ -1003,11 +1033,28 @@ gId('up').onclick = async () => {
 
 		const frames = [];
 		for (let i = 0; i < gF.length; i++) {
+			// put current GIF frame into tc
 			const id = new ImageData(new Uint8ClampedArray(gF[i].pixels), gI.width, gI.height);
 			tctx.putImageData(id, 0, 0);
+
+			// render this frame into the offscreen rotated canvas (no overlay)
+			rvc.clearRect(0, 0, rv.width, rv.height);
+			rvc.fillStyle = gId('bg').value;
+			rvc.fillRect(0, 0, rv.width, rv.height);
+			rvc.imageSmoothingEnabled = false;
+			rvc.save();
+			const dw = gI.width * iS, dh = gI.height * iS;
+			rvc.translate(pX + dw / 2, pY + dh / 2);
+			rvc.rotate(rot * Math.PI / 180);
+			rvc.drawImage(tc, -dw / 2, -dh / 2, dw, dh);
+			rvc.restore();
+
+			// sample the crop from the offscreen (already rotated) canvas into output size
 			cctx.fillStyle = gId('bg').value;
 			cctx.fillRect(0, 0, w, h);
-			cctx.drawImage(tc, (cr.x - pX) / iS, (cr.y - pY) / iS, cr.w / iS, cr.h / iS, 0, 0, w, h);
+			cctx.imageSmoothingEnabled = false;
+			cctx.drawImage(rv, cr.x, cr.y, cr.w, cr.h, 0, 0, w, h);
+
 			blackTh(cctx);
 			const fd = cctx.getImageData(0, 0, w, h);
 			frames.push({ data: fd.data, delay: gF[i].delay });