Image sampling

Image sampling is the process of investigating the status of an image prior to drawing it when the image is interpolated (enlarged) increasing the number of pixels, or decimated (shrunk) reducing the number of pixels. When an image is drawn on one device and then drawn on another device of a different resolution, it is interpolated or decimated as appropriate to maintain the same size on both devices. Interpolation and decimation also occur during rotate, scale, perspective, and translate operations on the image graphic.

The TImageSamplingControl::ESampleStyle field lets you specify a filtering method to control the appearance of the rendered image when it has been interpolated or decimated. The different filtering methods represent various quality and drawing speed tradeoffs. The filtering methods are described under the heading "Filtering methods" on page 182.

The TImageSamplingControl::SetAbyssColor function lets you specify a color to fill the abyss that can occur from drawing or transforming the image.See the heading "Filling the abyss" on page 183 for information on what causes an abyss to occur and how to fill it.

Figure 126 shows TImageSamplingControl and its related classes.

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