drawImage(
        tex, texWidth, texHeight,
        srcX, srcY, srcWidth, srcHeight,
        dstX, dstY, dstWidth, dstHeight, srcRotation) {
    var gl;
    var matrix, matrix2;
    var texMatrix;

    if (dstX === undefined) {
      dstX = srcX;
      srcX = 0;
    }
    if (dstY === undefined) {
      dstY = srcY;
      srcY = 0;
    }
    if (srcWidth === undefined) {
      srcWidth = texWidth;
    }
    if (srcHeight === undefined) {
      srcHeight = texHeight;
    }
    if (dstWidth === undefined) {
      dstWidth = srcWidth;
      srcWidth = texWidth;
    }
    if (dstHeight === undefined) {
      dstHeight = srcHeight;
      srcHeight = texHeight;
    }
    if (srcRotation === undefined) {
      srcRotation = 0;
    }

    gl = this._gl;
    gl.bindTexture(gl.TEXTURE_2D, tex);
    gl.useProgram(this._program);

    gl.bindBuffer(gl.ARRAY_BUFFER, this._positionBuffer);
    gl.enableVertexAttribArray(this._locations.position);
    gl.vertexAttribPointer(this._locations.position, 2, gl.FLOAT, false, 0, 0);
    gl.bindBuffer(gl.ARRAY_BUFFER, this._texcoordBuffer);
    gl.enableVertexAttribArray(this._locations.texcoord);
    gl.vertexAttribPointer(this._locations.texcoord, 2, gl.FLOAT, false, 0, 0);

    matrix = mat4.create();
    matrix2 = mat4.create();
    mat4.ortho(matrix, 0, 1000, 1000, 0, -1, 1);
    mat4.translate(matrix2, matrix, [dstX, dstY, 0]);
    mat4.copy(matrix, matrix2);
    mat4.scale(matrix2, matrix, [dstWidth, dstHeight, 1]);
    mat4.copy(matrix, matrix2);
    gl.drawingBufferHeight = 320;
    gl.uniformMatrix4fv(this._locations.matrix, false, matrix);
    texMatrix = mat4.create();
    mat4.fromScaling(texMatrix, [1 / texWidth, 1 / texHeight, 1]);
    mat4.translate(matrix2, texMatrix, [texWidth * 0.5, texHeight * 0.5, 0]);
    mat4.copy(texMatrix, matrix2);
    mat4.rotateZ(matrix2, texMatrix, srcRotation);
    mat4.copy(texMatrix, matrix2);
    mat4.translate(matrix2, texMatrix, [texWidth * -0.5, texHeight * -0.5, 0]);
    mat4.translate(texMatrix, matrix2, [srcX, srcY, 0]);
    mat4.scale(matrix2, texMatrix, [srcWidth, srcHeight, 1]);
    mat4.copy(texMatrix, matrix2);

    gl.uniformMatrix4fv(this._locations.textureMatrix, false, texMatrix);
    gl.uniform1i(this._locations.texture, 0);
    gl.drawArrays(gl.TRIANGLES, 0, 6);
  }