Adaptive screen and video coding scheme

A computer system, comprising one or more processing units and memory, that implements a video encoder configured to perform operations comprising:

• encoding an image to produce encoded data, wherein the image is partitioned into coding units (“CUs”), and wherein the encoding the image includes, for a given CU of the CUs:
• determining N major colors for pixel values of the given CU;
• assigning a color index value to each of the N major colors and an escape value;
• converting the pixel values of the given CU to color index values;
• encoding the color index values for the pixel values of the given CU using one or more of multiple modes, wherein, according to a prediction mode of the multiple modes, for a given pixel value among the pixel values of the given CU, the color index value for a neighboring pixel value is used as the color index value for the given pixel value;
• and
• for any of the pixel values of the given CU that is represented with the escape value, encoding the pixel value;
• and
• outputting the encoded data.

In a computer system that includes a video encoder, a method comprising:

• encoding an image to produce encoded data, wherein the image is partitioned into coding units (“CUs”), and wherein the encoding the image includes, for a given CU of the CUs:
• determining N major colors for pixel values of the given CU;
• assigning a color index value to each of the N major colors and an escape value;
• converting the pixel values of the given CU to color index values;
• encoding the color index values for the pixel values of the given CU using one or more of multiple modes, wherein, according to a prediction mode of the multiple modes, for a given pixel value among the pixel values of the given CU, the color index value for a neighboring pixel value is used as the color index value for the given pixel value;
• and
• for any of the pixel values of the given CU that is represented with the escape value, encoding the pixel value;
• and
• outputting the encoded data.

One or more computer-readable media having stored therein computer-executable instructions for causing one or more processing units, when programmed thereby, to perform operations comprising:

• encoding an image to produce encoded data, wherein the image is partitioned into coding units (“CUs”), and wherein the encoding the image includes, for a given CU of the CUs:
• determining N major colors for pixel values of the given CU;
• assigning a color index value to each of the N major colors and an escape value;
• converting the pixel values of the given CU to color index values;
• encoding the color index values for the pixel values of the given CU using one or more of multiple modes, wherein, according to a prediction mode of the multiple modes, for a given pixel value among the pixel values of the given CU, the color index value for a neighboring pixel value is used as the color index value for the given pixel value;
• and
• for any of the pixel values of the given CU that is represented with the escape value, encoding the pixel value;
• and
• outputting the encoded data