Compression techniques for burn-in statistics of organic light emitting diode (OLED) displays
Disclosed herein are techniques for pre-processing image data for compression, e.g., image data that represents burn-in statistics for a display device. The techniques can involve receiving the image data, where the image data comprises a plurality of pixels, and each pixel of the plurality of pixels comprises at least two sub-pixel values. Next, each pixel of the plurality of pixels is quantized to produce a plurality of modified pixels. Subsequently, a series of operations are performed against each modified pixel of the plurality of modified pixels, including (1) applying an invertible transformation against the modified pixel, (2) applying a predictive coding against the modified pixel, and (3) applying an encoding of the modified pixel into a buffer as a data stream. The buffer is then compressed (as the modified pixels are serially encoded into the buffer) to produce compressed outputs that are joined together to produce a compressed image.
1. A method for pre-processing image data for compression, the method comprising, at a computing device:
receiving the image data, wherein the image data comprises a plurality of pixels, and each pixel of the plurality of pixels comprises at least two sub-pixel values;
quantizing, for each pixel of the plurality of pixels, the at least two sub-pixel values to produce a plurality of modified pixels; and
for each modified pixel of the plurality of modified pixels:
applying an invertible transformation to the at least two sub-pixel values for the modified pixel to produce an equal number of transformed sub-pixel values,
applying a predictive coding to at least one of the transformed sub-pixel values of the modified pixel, wherein applying the predictive coding involves establishing a differential value by subtracting a corresponding and previously-processed sub-pixel value from the at least one of the transformed sub-pixel values,
encoding the differential value into two corresponding bytes,
encoding each of the other transformed sub-pixel values different from the at least one of the transformed sub-pixel values into respective two corresponding bytes,
serially storing the corresponding bytes as a data stream into a buffer, and compressing the data stream in the buffer.
2. The method of claim 1 , wherein the at least two sub-pixel values include a blue sub-pixel value and a red sub-pixel value, and applying the invertible transformation comprises:
subtracting the blue sub-pixel value from the red sub-pixel value to produce a difference, and
replacing the blue sub-pixel value with the difference.
3. The method of claim 1 , wherein the at least two sub-pixel values include a first green sub-pixel value and a second green sub-pixel value, and applying the invertible transformation comprises:
subtracting the second green sub-pixel value from the first green sub-pixel value to produce a difference, and
replacing the second green sub-pixel value with the difference.
4. The method of claim 1 , wherein corresponding sub-pixel values of the plurality of pixels are quantized using a different quantizer.
5. The method of claim 1 , wherein:
the differential value is comprised of sixteen bits, wherein one bit of the sixteen bits is a sign bit, and fifteen of the sixteen bits are magnitude bits, and
encoding the differential value into two corresponding bytes comprises:
placing, into a first byte of the two corresponding bytes, seven of the least significant bits of the magnitude bits, followed by the sign bit, and
placing, into a second byte of the two corresponding bytes, eight of the most significant bits of the magnitude bits.
6. The method of claim 5 , wherein serially storing the corresponding bytes as the data stream into the buffer comprises:
serially placing the first bytes of each of the two corresponding bytes into a leading position within data stream, and
serially placing the second bytes of each of the two corresponding bytes into a trailing position within the data stream.
7. The method of claim 1 , wherein compressing the data stream in the buffer produces a compressed output, and the compressed outputs for each modified pixel of the plurality of modified pixels are combined together to produce a compressed image.
8. A non-transitory computer readable storage medium configured to store instructions that, when executed by a processor included in a computing device, cause the computing device to pre-process image data for compression, by carrying out steps that include:
receiving the image data, wherein the image data comprises a plurality of pixels, and each pixel of the plurality of pixels comprises at least two sub-pixel values;
quantizing, for each pixel of the plurality of pixels, the at least two sub-pixel values to produce a plurality of modified pixels; and
for each modified pixel of the plurality of modified pixels:
applying an invertible transformation to the at least two sub-pixel values for the modified pixel to produce an equal number of transformed sub-pixel values,
applying a predictive coding to at least one of the transformed sub-pixel values of the modified pixel, wherein applying the predictive coding involves establishing a differential value by subtracting a corresponding and previously-processed sub-pixel value from the at least one of the transformed sub-pixel values,
encoding the differential value into two corresponding bytes,
encoding each of the other transformed sub-pixel values different from the at least one of the transformed sub-pixel values into respective two corresponding bytes,
serially storing the corresponding bytes as a data stream into a buffer, and compressing the data stream in the buffer.
9. The non-transitory computer readable storage medium of claim 8 , wherein the at least two sub-pixel values include a blue sub-pixel value and a red sub-pixel value, and applying the invertible transformation comprises:
subtracting the blue sub-pixel value from the red sub-pixel value to produce a difference, and
replacing the blue sub-pixel value with the difference.
10. The non-transitory computer readable storage medium of claim 8 , wherein the at least two sub-pixel values include a first green sub-pixel value and a second green sub-pixel value, and applying the invertible transformation comprises:
subtracting the second green sub-pixel value from the first green sub-pixel value to produce a difference, and
replacing the second green sub-pixel value with the difference.
11. The non-transitory computer readable storage medium of claim 8 , wherein corresponding sub-pixel values of the plurality of pixels are quantized using a different quantizer.
12. The non-transitory computer readable storage medium of claim 8 , wherein:
the differential value is comprised of sixteen bits, wherein one bit of the sixteen bits is a sign bit, and fifteen of the sixteen bits are magnitude bits, and
encoding the differential value into two corresponding bytes comprises:
placing, into a first byte of the two corresponding bytes, seven of the least significant bits of the magnitude bits, followed by the sign bit, and
placing, into a second byte of the two corresponding bytes, eight of the most significant bits of the magnitude bits.
13. The non-transitory computer readable storage medium of claim 12 , wherein serially storing the corresponding bytes as the data stream into the buffer comprises:
serially placing the first bytes of each of the two corresponding bytes into a leading position within data stream, and
serially placing the second bytes of each of the two corresponding bytes into a trailing position within the data stream.
14. The non-transitory computer readable storage medium of claim 8 , wherein compressing the data stream in the buffer produces a compressed output, and the compressed outputs for each modified pixel of the plurality of modified pixels are combined together to produce a compressed image.
15. A computing device configured to pre-process image data for compression, the computing device comprising:
a processor; and
a memory configured to store instructions that, when executed by the processor, cause the computing device to:
receive the image data, wherein the image data comprises a plurality of pixels, and each pixel of the plurality of pixels comprises at least two sub-pixel values;
quantize, for each pixel of the plurality of pixels, the at least two sub-pixel values to produce a plurality of modified pixels; and
for each modified pixel of the plurality of modified pixels:
apply an invertible transformation to the at least two sub-pixel values for the modified pixel to produce an equal number of transformed sub-pixel values,
apply a predictive coding to at least one of the transformed sub-pixel values of the modified pixel, wherein applying the predictive coding involves establishing a differential value by subtracting a corresponding and previously-processed sub-pixel value from the at least one of the transformed sub-pixel values,
encode the differential value into two corresponding bytes,
encode each of the other transformed sub-pixel values different from the at least one of the transformed sub-pixel values into respective two corresponding bytes,
serially store the corresponding bytes as a data stream into a buffer, and compress the data stream in the buffer.
16. The computing device of claim 15 , wherein the at least two sub-pixel values include a blue sub-pixel value and a red sub-pixel value, and applying the invertible transformation comprises:
subtracting the blue sub-pixel value from the red sub-pixel value to produce a difference, and
replacing the blue sub-pixel value with the difference.
17. The computing device of claim 15 , wherein the at least two sub-pixel values include a first green sub-pixel value and a second green sub-pixel value, and applying the invertible transformation comprises:
subtracting the second green sub-pixel value from the first green sub-pixel value to produce a difference, and
replacing the second green sub-pixel value with the difference.
18. The computing device of claim 15 , wherein:
the differential value is comprised of sixteen bits, wherein one bit of the sixteen bits is a sign bit, and fifteen of the sixteen bits are magnitude bits, and
encoding the differential value into two corresponding bytes comprises:
placing, into a first byte of the two corresponding bytes, seven of the least significant bits of the magnitude bits, followed by the sign bit, and
placing, into a second byte of the two corresponding bytes, eight of the most significant bits of the magnitude bits.
19. The computing device of claim 18 , wherein serially storing the corresponding bytes as the data stream into the buffer comprises:
serially placing the first bytes of each of the two corresponding bytes into a leading position within data stream, and
serially placing the second bytes of each of the two corresponding bytes into a trailing position within the data stream.
20. The computing device of claim 15 , wherein compressing the data stream in the buffer produces a compressed output, and the compressed outputs for each modified pixel of the plurality of modified pixels are combined together to produce a compressed image.