WebGLRenderer: Allow zero values for x,y in .readRenderTargetPixels

src/renderers/WebGLRenderer.js

@@ -3385,7 +3385,7 @@ THREE.WebGLRenderer = function ( parameters ) {
 
 					// the following if statement ensures valid read requests (no out-of-bounds pixels, see #8604)
 
-					if ( ( x > 0 && x <= ( renderTarget.width - width ) ) && ( y > 0 && y <= ( renderTarget.height - height ) ) ) {
+					if ( ( x >= 0 && x <= ( renderTarget.width - width ) ) && ( y >= 0 && y <= ( renderTarget.height - height ) ) ) {
 
 						_gl.readPixels( x, y, width, height, paramThreeToGL( texture.format ), paramThreeToGL( texture.type ), buffer );