Hi I was just hoping someone could please explain why *Row has to be a uint8 instead of a uint32 and why then *Pixel is a uint32. Thanks
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | uint8 *Row = Buffer->Memory + MinX * Buffer->BytesPerPixel + MinY * Buffer->Pitch
for(int Y = MinY; Y < MaxY; Y++)
{
uint32 *Pixel = (uint32 *)Row;
for(int X = MinX; X < MaxX; X++)
{
*Pixel++ = Color;
}
Row += Buffer->Pitch;
}
|
So that Row += Buffer->Pitch; will work.
pointer arithmetic will automatically multiply the size of the thing pointer ad with the offsets you add and subtract to it. uint8 is the same granularity in which Pitch is provided so it makes sense to use that.
pointer arithmetic will automatically multiply the size of the thing pointer ad with the offsets you add and subtract to it. uint8 is the same granularity in which Pitch is provided so it makes sense to use that.
You may find some more informations on this thread.
1 2 3 4 | fake Buffer->Memory 0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n |
you can pretend that each element of the array above is the size uint8
so from the start of the array, 0, going 4 uint8's in gets you to 4
1 | [start here]0, 1, 2, 3, [end here]4 |
1 | uint8 *arraystart + 4 = 4 |
and from
1 | (uint8 *)(j's position) + 4 = n |
since a uint32 is equal to 4 uint8's, it represents 4 elements in the array.
from the start of the array going 1 uint32 further gets you to 4
1 | (uint32 *)arraystart + 1 = 4 |
pitch = amount to get to the next row but under where the old position was
pitch = 8
row is a uint8 pointer type
1 | uint8 *Row |
if row were a uint32 * then adding pitch would add pitch * 4 = 32
and would go outside of the array above, the point being it's not working as a pitch then
with the uint32 *Pixel, it's the same logic, you're accessing 4 elements at a time.
1 | [0, 1, 2 , 3], [4, 5, 6, 7] ... [g, h, i, j] ... |