Fix download images to match live gl3d plot

src/plots/gl3d/scene.js

@@ -989,6 +989,37 @@ proto.updateFx = function(dragmode, hovermode) {
  scene.fullSceneLayout.hovermode = hovermode;
 };
 
+function flipPixels(pixels, w, h) {
+ for(var i = 0, q = h - 1; i < q; ++i, --q) {
+ for(var j = 0; j < w; ++j) {
+ for(var k = 0; k < 4; ++k) {
+ var a = 4 * (w * i + j) + k;
+ var b = 4 * (w * q + j) + k;
+ var tmp = pixels[a];
+ pixels[a] = pixels[b];
+ pixels[b] = tmp;
+ }
+ }
+ }
+}
+
+function correctRGB(pixels, w, h) {
+ for(var i = 0; i < h; ++i) {
+ for(var j = 0; j < w; ++j) {
+ var k = 4 * (w * i + j);
+
+ var a = pixels[k + 3]; // alpha
+ if(a > 0) {
+ var q = 255 / a;
+
+ for(var l = 0; l < 3; ++l) { // RGB
+ pixels[k + l] = Math.min(q * pixels[k + l], 255);
+ }
+ }
+ }
+ }
+}
+
 proto.toImage = function(format) {
  var scene = this;
 
@@ -1007,17 +1038,8 @@ proto.toImage = function(format) {
 
  var pixels = new Uint8Array(w * h * 4);
  gl.readPixels(0, 0, w, h, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
-
- // Flip pixels
- for(var j = 0, k = h - 1; j < k; ++j, --k) {
- for(var i = 0; i < w; ++i) {
- for(var l = 0; l < 4; ++l) {
- var tmp = pixels[4 * (w * j + i) + l];
- pixels[4 * (w * j + i) + l] = pixels[4 * (w * k + i) + l];
- pixels[4 * (w * k + i) + l] = tmp;
- }
- }
- }
+ flipPixels(pixels, w, h);
+ correctRGB(pixels, w, h);
 
  var canvas = document.createElement('canvas');
  canvas.width = w;