There's nothing to blur, because you're not creating a raster image. The only raster image is the screenshot, and blurring a screenshot makes even less sense.
Bear in mind that you appear to be trying to create an image of a particular size (2268x3402), but the rendered image size is completely arbitrary. Not even the aspect ratio is preserved. Given that the axis rulers are hidden, I don't see why the image size even matters here. If you want a pseudocolor image of a particular size, taking a screenshot of the entire figure is not going to let you do that.
Attached is a version which does the work without using fill(). The variable thisT is a 2268x3402 array of temperature data. For sake of consistency with the demonstrated workflow, this 2D data is rendered with imagesc(), a colorbar and title, and a screenshot is saved. The image geometry is still lost because the result is a screenshot.
If you want an actual 2268x3402 pseudocolor image, then that's a different story. Attached is another copy which generates plain images instead of screenshots.
In both cases, the graduation is purely a result of the linear interpolation from 3x9 to 2268x3402. Whether that makes technical sense or not, I don't know. Since we're working with raster images, you could always do the interpolation in other ways, or you could do other sorts of filtering after resizing.
Oh. I forgot to mention that I ran the code through a translator. Given that the translator returned hilariously invalid code the first time, I'm not inclined to try to translate it back again.
