TDA4VM: mosaic

Hi! I use mosaic node to show srv view and front view. There are two problems.

1. Srv image is 960 *960, I use mosaic node to show roi view of srv image. Here is my code. As you see, 

    imgMosaicObj->params.windows[idx].startX = 0;
    imgMosaicObj->params.windows[idx].startY = 0;
    imgMosaicObj->params.windows[idx].width = 540;
    imgMosaicObj->params.windows[idx].height = 960;
    imgMosaicObj->params.windows[idx].input_select = 1;
    imgMosaicObj->params.windows[idx].channel_select = 0;
    imgMosaicObj->params.windows[idx].enable_roi = 1;
    imgMosaicObj->params.windows[idx].roiStartX = 180;
    imgMosaicObj->params.windows[idx].roiStartY = 180;
    imgMosaicObj->params.windows[idx].roiWidth = 600;
    imgMosaicObj->params.windows[idx].roiHeight = 960;

2. Because, I found the problem and want to achieve the task. I want to add node of vxCreateImageFromROI. The input of mosaic node is vx_object_array, use the code below, and got something wrong. I don't know how to convert vx_image to vx_object_array.

vx_image image_ROI = vxCreateImageFromROI(input_image, &roi_rect);
image_ROI = (vx_image)vxGetObjectArrayItem((vx_object_array)obj->image_ROI_array, 0);