ImageBrush Class

Placement. The image is in its own coordinates: its pixel (i, j) covers the square from (i, j) to (i + 1, j + 1), the pixel at the top-left corner of the frame being at the origin, and ImageBrush.Transform places it on the canvas. Without transformation, the pixels of the image are on the pixels of the canvas. ImageBrush.SourceRegion limits the image to some of its pixels, which stay where they are; ImageBrush.WrapModeX and ImageBrush.WrapModeY give the colors around them.

Colors. The color of a pixel of the canvas is the color of the image at the position its center comes from. With ImageSampling.Bilinear, the four pixels of the image around that position are interpolated at 16 bits, on alpha-premultiplied values, and the result is rounded to nearest; where the centers of the pixels of the image are on the centers of the pixels of the canvas (no transformation, or a translation by whole pixels), the colors are those of the image, exactly. The colors are then converted to the pixel format of the canvas like any brush color: they are sample values, and no color profile is applied. Floating-point images retain their range and precision on floating-point canvases. On integer canvases their samples are read as 16-bit colors: a sample outside [0, 1] or that is not a number has none, and the drawing that reads it throws an UnsupportedImageFeatureException instead of clipping it.

An image drawn smaller than it is skips pixels: each pixel of the canvas reads four pixels of the image at most. ImageSampling.Smooth reads every pixel a pixel of the canvas covers instead, for a result without aliasing, and ImageSampling.Box averages them; reduce an image that is drawn many times first (Resize).

Lifetime. The brush refers to the frame and does not own it. The pixels are read when a shape is drawn: the frame must still belong to a live image, and must not be one of the frames being drawn on.