Re: A85: Find_pixel
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Re: A85: Find_pixel
On Fri, 09 Jan 1998 18:39:19 -0600, you wrote:
>
>When you call find_pixel, what exactly gets returned? HL points to
>the first byte containing (b,c), right? But what is returned in the A
>register?
>
Register a has the bit mask of the pixel you are looking for. To find
what is going to be in the a register, you do the modulus operation
(gives the remainder of a division). To find the value in a you have
x-position MODULUS 8 (8 is #pixels in 1 byte) which gives a number
0-7. For the remainder being 0, the value in a = 10000000b, for 1 a =
01000000b, for 2 a = 00100000b, etc, for 7 a = %00000001b. So this
tells the specific pixel in the byte (byte is in hl).
-mike pearce
mgp4007@omega.uta.edu
References: