 4) {
        for (var jj = 0; jj < 4; ++jj) {
          data[ii + jj] = color[jj];
        }
    }
    gl.bindTexture(gl.TEXTURE_2D, tex_read);
    gl.texImage2D(gl.TEXTURE_2D, 0, readbufferFormat, size, size, 0, gl.RGBA, gl.UNSIGNED_BYTE, data);
    gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fbo_read);
    gl.framebufferTexture2D(gl.READ_FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex_read, 0);
    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "setup read framebuffer should succeed");

    // Create multiple te