Accusoft TwainPRO 9
TP_PngFilter Enumeration
| AccusoftTwainPro9 ActiveX DLL : TP_PngFilter Enumeration |
| Member | Value | Description |
|---|---|---|
| TP_PngFilter_Average | 3 | The Average filter uses the average of the two neighboring pixels (left and above) to predict the value of a pixel. |
| TP_PngFilter_None | 0 | Fastest, no filter is used. |
| TP_PngFilter_Optimal | 5 | Optimal compressed file size, at the expense of speed. |
| TP_PngFilter_Paeth | 4 | The Paeth filter computes a simple linear function of the three neighboring pixels (left, above, upper left), then chooses as predictor the neighboring pixel closest to the computed value. This technique is due to Alan W. Paeth. |
| TP_PngFilter_Sub | 1 | The Sub filter transmits the difference between each byte and the value of the corresponding byte of the prior pixel. |
| TP_PngFilter_Up | 2 | The Up filter is just like the Sub filter except that the pixel immediately above the current pixel, rather than just to its left, is used as the predictor. |