JPEG processing engine for low profile systems

1. A method executed by a computer system for processing minimum coded units (MCUs) in a Joint Photographic Expert Group (JPEG) bit stream representing an image to transform the image, comprising:

generating a data structure storing MCU block numbers of the MCUs, MCU block coordinates of the MCUs in the image, and MCU block editing lists of the MCUs;

receiving one or more editing operations to be applied to one or more of the MCUs;

subsequent to said receiving, saving the editing operations to one or more of the MCU block editing lists of the MCUs affected by the editing operations; and

subsequent to said saving, generating a new JPEG bit stream, comprising:

retrieving the MCUs from the JPEG bit stream; and

for each retrieved MCU, decoding the retrieved MCU, processing the retrieved MCU according to any editing operations in a corresponding MCU block editing list, encoding the retrieved MCU, and saving the retrieved MCU in the new JPEG bit stream.

2. A method executed by a computer system for processing minimum coded units (MCUs) in a Joint Photographic Expert Group (JPEG) bit stream representing an image to transform the image, comprising:

generating a data structure storing MCU block numbers of the MCUs, MCU block coordinates of the MCUs in the image, and MCU block editing lists of the MCUs;

receiving an editing operation to be applied to a group of the MCUs;

saving the editing operation to a group of the MCU block editing lists of the group of the MCUs affected by the editing operation;

receiving another editing operation to the image, wherein the editing operation is a cropping of the image;

saving the cropping operation to another group of the MCU block editing lists of another group of the MCUs being cropped out of the image; and

performing editing operations in the MCU block editing lists excluding said another group of the MCU block editing lists.

3. The method of claim 1 , wherein when one of the editing operations comprises a rotation, the method further comprises calculating new MCU block coordinates for the MCUs based on the rotation.

4. The method of claim 3 , further comprising:

determining a new order of the MCUs in the new JPEG bit stream after the rotation based on the new MCU block coordinates.

5. The method of claim 4 , wherein said generating a new JPEG bit stream further comprises:

from an index storing bit offsets from a start of the JPEG bit stream of the MCUs, reading the bit offsets of the MCUs;

from the bit offsets, determining the boundaries of the MCUs in the JPEG bit stream; and

wherein said retrieving the MCUs from the JPEG bit stream occurs in the new order.

6. The method of claim 1 , wherein said generating a new JPEG bit stream further comprises:

from an index storing bit offsets from a start of the JPEG bit stream of the MCUs, reading the bit offsets of the MCUs; and

from the bit offsets, determining the boundaries of the MCUs in the JPEG bit stream for said retrieving.

7. A computer readable storage medium encoded with instructions for processing minimum coded units (MCUs) in a Joint Photographic Expert Group (JPEG) bit stream representing a image to transform the image, the instructions comprising:

generating a data structure storing MCU block numbers of the MCUs, MCU block coordinates of the MCUs in the image, and MCU block editing lists of the MCUs;

receiving one or more editing operations to be applied to one or more of the MCUs;

subsequent to said receiving, saving the editing operations to one or more of the MCU block editing lists of the MCUs affected by the editing operation; and

subsequent to said saving, generating a new JPEG bit stream, comprising:

retrieving the MCUs from the JPEG bit stream; and

for each retrieved MCU, decoding the retrieved MCU, processing the retrieved MCU according to any editing operations in a corresponding MCU block editing list, encoding the retrieved MCU, and saving the retrieved MCU in the new JPEG bit stream.

8. A computer readable storage medium encoded with instructions for processing minimum coded units (MCUs) in a Joint Photographic Expert Group (JPEG) bit stream representing a image to transform the image, the instructions comprising:

generating a data structure storing MCU block numbers of the MCUs, MCU block coordinates of the MCUs in the image, and MCU block editing lists of the MCUs;

receiving an editing operation to be applied to a group of the MCUs;

saving the editing operation to a group of the MCU block editing lists of the group of the MCUs affected by the editing operation;

receiving another editing operation to the image, wherein the editing operation is a cropping of the image;

saving the cropping operation to another group of the MCU block editing lists of another group of the MCUs being cropped out of the image; and

performing editing operations in the MCU block editing lists excluding said another group of the MCU block editing lists.

9. The medium of claim 7 , wherein when one of the editing operations comprises a rotation, the instructions farther comprise calculating new MCU block coordinates for the MCUs based on the rotation.

10. The medium of claim 9 , wherein the instructions further comprise:

determining a new order of the MCUs in the new JPEG bit stream after the rotation based on the new MCU block coordinates.

11. The medium of claim 10 , wherein said generating a new JPEG bit stream further comprises:

from an index storing bit offsets from a start of the JPEG bit stream of the MCUs, reading the bit offsets of the MCUs;

from the bit offsets, determining the boundaries of the MCUs in the JPEG bit stream; and

wherein said retrieving the MCUs from the JPEG bit stream occurs in the new order.

12. The medium of claim 7 , wherein said generating a new JPEG bit stream further comprises:

from an index storing bit offsets from a start of the JPEG bit stream of the MCUs, reading the bit offsets of the MCUs; and

from the bit offsets, determining the boundaries of the MCUs in the JPEG bit stream for said retrieiving.