Graphics data processing apparatus having image operations with transparent color having a selectable number of bits

• US 4,752,893 A
• Filed: 11/06/1985
• Issued: 06/21/1988
• Est. Priority Date: 11/06/1985
• Status: Expired

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Asal, Michael D., Guttag, Karl M., Preston, Thomas
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): Herndon, H.R.
• Application Number:
  US06/795,382
• Time in Patent Office: 958 Days
• Field of Search: 364/518-522, 340/701, 340/703, 340/721, 340/724, 340/729, 340/747, 340/750, 340/798, 340/799, 358/200
• US Class Current: 345/440
• CPC Class Codes: G09G 2340/10 Mixing of images, i.e. displayed pixel being the result of an operation, e.g. adding, on the corresponding input pixels
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory

Abstract

A graphics data processing apparatus having graphic image operations on two images. Two graphic images are formed into a single combined image based upon a predetermined combination of the multibit color codes representing corresponding pixels of the two images. A transparent color code is permitted for the first of the graphic images. The combination of a transparent color code from the first graphic image with any color code from the second graphic image yields the color code of the second graphic image. This innovation enables the use of color codes having selectable numbers of bits set by the number stored in a pixel size register. In particular the transparent color code, which is detected by a transparent color code detection device independent of the image operation, has a selectable number of bits set by the pixel size register in a manner like any other color code. This enables the same graphics data processing apparatus to be applicable to a wide variety of applications having images using differing lengths of color codes while preserving the transparency function.

Claims

1. A graphics image processing apparatus comprising:

a pixel size register for storing a number indicative of the number of bits per pixel;

a first image memory for storing a first array of pixels, each pixel represented by a data code having the number of bits indicated by said pixel size register, one of said data codes corresponding to a transparent data code;

a second image memory for storing a second array of pixels, each pixel represented by a data code; and

a transparent data code detector connected to said first image memory for detecting said transparent data code stored by a pixel in said first array; and

an array image operator connected to said first and second image memories and transparent data code detector for performing an image operation to generate a third array of pixels from said first and second array of pixels, each pixel of said third array represented by a combination of the data codes representing corresponding pixels of said first and second arrays of pixels, wherein, for each pixel of said first array containing said transparent data code, the corresponding pixel of said third array of pixels is represented by the data code of the corresponding pixel in said second array of pixels.

2. A graphics data processing apparatus as claimed in claim 1, wherein:

said array image operator further stores said third array of pixels in said second image memory, each pixel of said third array of pixels replacing the corresponding pixel of said second array of pixels.

3. A graphics image processing apparatus as claimed in claim 1, wherein:

said transparent data code is represented by a data word where all bits are "0'"'"'s".

4. A graphics image processing apparatus as claimed in claim 1, wherein:

said image operation is a logical combination of the individual bits of the data code of the pixel in said first array and the data code of the corresponding pixel in said second array.

5. A graphics image processing apparatus as claimed in claim 1, wherein:

said image operation is an arithmetic combination dependent upon the numbers represented by the data code of the pixel in said first array and by the data code of the corresponding pixel in said second array.

6. A graphics image processing apparatus comprising:

a pixel size register for storing a number indicative of the number of bits per pixel;

a memory including a data portion for storing a source image represented by a first array of pixels, each pixel represented by a data code having the number of bits indicated by said pixel size register, one of said data codes corresponding to a transparent data code, and including a display portion for storing a display image represented by a second array of pixels, each pixel represented by data code;

a transparent data code detector connected to said memory for detecting a transparent data code stored by a pixel of said source image; and

an array image operator connected to said memory and said transparent color code detector for performing an image operation to generate a third array of pixels, each pixel of said third array represented by a combination of the data codes representing corresponding pixels of said first and second arrays of pixels, wherein, for each pixel of said first array containing said transparent data code, the corresponding pixel of said third array of pixels is represented by the data code of the corresponding pixel in said second array of pixels.

7. A graphics image processing apparatus as claimed in claim 6, wherein:

said array image operator further stores said third array of pixels in said display portion of said memory, each pixel of said third array of pixels replacing the corresponding pixel of said second array of pixels.

8. A graphics image processing apparatus as claimed in claim 6, wherein:

said transparent data code is represented by a data word where all bits are "0'"'"'s".

9. A graphics image processing apparatus as claimed in claim 6, wherein:

said image operation is a logical combination of the individual bits of the data code of the pixel in said source image and the data code of the corresponding pixel in said display image.

10. A graphics image processing apparatus as claimed in claim 6, wherein:

said image operation is an arithmetic combination of the numbers represented by the data code of the pixel in said source image and by the data code ofthe corresponding pixel in said display image.