Previewing dynamic images and expressions

1. A computer-implemented method, the method comprising:

determining, by one or more processors, that a location of a preview image of a dynamic image is not stored in a memory;

transmitting, by the one or more processors, in response to determining that the preview image is not stored in the memory, a request for a frame number of at least one static image included in the dynamic image to a network address;

generating, by the one or more processors, a designated frame number for the at least one static image based on a rule of combining an issued frame number received from the network address and a default frame number of a displaying application;

extracting, by the one or more processors, the at least one static image having the designated frame number;

displaying, by the one or more processors, the at least one static image having the designated frame number as the preview image to a user;

receiving, by the one or more processors, a selection, by a user, of the at least one static image;

requesting and receiving, by the one or more processors, an expression package that comprises frames of the dynamic image; and

providing, by the one or more processors, the dynamic image, for display to the user, the dynamic image comprising executing the expression package, comprising beginning the dynamic image at a selected image having the designated frame number.

2. The computer-implemented method of claim 1 , wherein determining the location of the preview image of the dynamic image is not stored in the memory further comprises obtaining the network address of the expression package that comprises the dynamic image.

3. The computer-implemented method of claim 1 , wherein the designated frame number comprises an issued frame number of the dynamic image, a locally stored built-in frame number of the dynamic image, or a default frame number.

4. The computer-implemented method of claim 1 , further comprising determining whether the issued frame number is received from the network address within a predetermined time.

5. The computer-implemented method of claim 4 , further comprising, in response to determining that the issued frame number is received from the network address within the predetermined time, determining that the issued frame number is greater than a maximum frame number of the dynamic image.

6. The computer-implemented method of claim 4 , further comprising, in response to determining that the issued frame number is not received from the network address within the predetermined time, setting a last frame of static image data of the dynamic image as the designated frame number for the preview image.

7. The computer-implemented method of claim 1 , wherein extracting the at least one static image having the designated frame number further comprises:

generating a preview image corresponding to the at least one static image; and

caching the preview image in the memory.

8. The computer-implemented method of claim 1 , wherein the dynamic image comprises a dynamic expression in an expression package.

9. The computer-implemented method of claim 8 , wherein the expression package comprises an installation file comprising a built-in frame number that corresponds to the dynamic expression and used as the designated frame number.

10. A non-transitory, computer-readable medium storing one or more instructions executable by a computer system to perform operations comprising:

determining that a location of a preview image of a dynamic image is not stored in a memory;

transmitting in response to determining that the preview image is not stored in the memory, a request for a frame number of at least one static image included in the dynamic image to a network address;

generating a designated frame number for the at least one static image based on a rule of combining an issued frame number from the network address and a default frame number of a displaying application;

extracting the at least one static image having the designated frame number;

displaying the at least one static image having the designated frame number as the preview image to a user;

receiving a selection, by a user, of the at least one static image;

requesting and receiving an expression package that comprises frames of the dynamic image; and

providing the dynamic image, for display to the user, the dynamic image comprising executing the expression package, comprising beginning the dynamic image at a selected image having the designated frame number.

11. The computer-readable medium of claim 10 , wherein determining the location of the preview image of the dynamic image is not stored in the memory further comprises obtaining the network address of the expression package that comprises the dynamic image.

12. The computer-readable medium of claim 10 , wherein the designated frame number comprises an issued frame number of the dynamic image, a locally stored built-in frame number of the dynamic image, or a default frame number.

13. The computer-readable medium of claim 10 , further comprising determining whether the issued frame number is received from the network address within a predetermined time.

14. The computer-readable medium of claim 13 , further comprising, in response to determining that the issued frame number is received from the network address within the predetermined time, determining that the issued frame number is greater than a maximum frame number of the dynamic image.

15. The computer-readable medium of claim 14 , further comprising, in response to determining that the issued frame number is not received from the network address within the predetermined time, setting a last frame of static image data of the dynamic image as the designated frame number for the preview image.

16. The computer-readable medium of claim 10 , wherein extracting the at least one static image having the designated frame number further comprises:

generating a preview image corresponding to the at least one static image; and

caching the preview image in the memory.

17. The computer-readable medium of claim 10 , wherein the dynamic image comprises a dynamic expression in an expression package.

18. The computer-readable medium of claim 17 , where the expression package comprises an installation file comprising a built-in frame number that corresponds to the dynamic expression and used as the designated frame number.

19. A computer-implemented system, comprising:

one or more computers; and

one or more computer memory devices interoperably coupled with the one or more computers and having tangible, non-transitory, machine-readable media storing one or more instructions that, when executed by the one or more computers, perform one or more operations comprising:

determining that a location of a preview image of a dynamic image is not stored in a memory;

transmitting in response to determining that the preview image is not stored in the memory, a request for a frame number of at least one static image included in the dynamic image to a network address;

generating a designated frame number for the at least one static image based on a rule of combining an issued frame number from the network address and a default frame number of a displaying application;

extracting the at least one static image having the designated frame number;

displaying the at least one static image having the designated frame number as the preview image to a user;

receiving a selection, by a user, of the at least one static image;

requesting and receiving an expression package that comprises frames of the dynamic image; and

providing the dynamic image, for display to the user, the dynamic image comprising executing the expression package, comprising beginning the dynamic image at a selected image having the frame number.

20. The computer-implemented system of claim 19 , wherein determining the location of the preview image of the dynamic image is not stored in the memory further comprises obtaining the network address of the expression package that comprises the dynamic image.