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Reviewed ImageDrawLine() formating

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Ray 2021-07-23 23:32:20 +02:00
parent ff2b8d6db1
commit 00911b0842
1 changed files with 35 additions and 45 deletions
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64
src/textures.c
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@ -2423,22 +2423,20 @@ void ImageDrawLine(Image *dst, int startPosX, int startPosY, int endPosX, int en
// https://classic.csunplugged.org/wp-content/uploads/2014/12/Lines.pdf // https://classic.csunplugged.org/wp-content/uploads/2014/12/Lines.pdf
int changeInX = (endPosX - startPosX); int changeInX = (endPosX - startPosX);
int abs_changeInX = (changeInX < 0)? -changeInX : changeInX; int absChangeInX = (changeInX < 0)? -changeInX : changeInX;
int changeInY = (endPosY - startPosY); int changeInY = (endPosY - startPosY);
int abs_changeInY = (changeInY < 0)? -changeInY : changeInY; int absChangeInY = (changeInY < 0)? -changeInY : changeInY;
int startU, startV, endU, V_step; // Substitutions, either U = X, V = Y or vice versa. See loop at end of function int startU, startV, endU, stepV; // Substitutions, either U = X, V = Y or vice versa. See loop at end of function
//int endV; // This is not needed, but to aid understanding it is left in the code below. //int endV; // Not needed but left for better understanding, check code below
int A, B, P; // See linked paper above, explained down in the main loop
int reversedXY = (absChangeInY < absChangeInX);
int A, B, P; // See linked paper above. Explained down in the main loop. if (reversedXY)
int is_x_y_reversed = (abs_changeInY < abs_changeInX);
if (is_x_y_reversed)
{ {
A = 2*abs_changeInY; A = 2*absChangeInY;
B = A - 2*abs_changeInX; B = A - 2*absChangeInX;
P = A - abs_changeInX; P = A - absChangeInX;
if (changeInX > 0) if (changeInX > 0)
{ {
@ -2454,20 +2452,20 @@ void ImageDrawLine(Image *dst, int startPosX, int startPosY, int endPosX, int en
endU = startPosX; endU = startPosX;
//endV = startPosY; //endV = startPosY;
// since start and end are reversed: // Since start and end are reversed
changeInX = -changeInX; changeInX = -changeInX;
changeInY = -changeInY; changeInY = -changeInY;
} }
V_step = (changeInY < 0)? -1 : 1; stepV = (changeInY < 0)? -1 : 1;
ImageDrawPixel(dst, startU, startV, color); // At this point they are correctly ordered... ImageDrawPixel(dst, startU, startV, color); // At this point they are correctly ordered...
} }
else // all X and Y are reversed in here: else
{ {
A = 2*abs_changeInX; A = 2*absChangeInX;
B = A - 2*abs_changeInY; B = A - 2*absChangeInY;
P = A - abs_changeInY; P = A - absChangeInY;
if (changeInY > 0) if (changeInY > 0)
{ {
@ -2483,36 +2481,28 @@ void ImageDrawLine(Image *dst, int startPosX, int startPosY, int endPosX, int en
endU = startPosY; endU = startPosY;
//endV = startPosX; //endV = startPosX;
// since start and end are reversed: // Since start and end are reversed
changeInX = -changeInX; changeInX = -changeInX;
changeInY = -changeInY; changeInY = -changeInY;
} }
V_step = (changeInX < 0)? -1 : 1; stepV = (changeInX < 0)? -1 : 1;
ImageDrawPixel(dst, startV, startU, color); // ... but need to be reversed here. Repeated in the main loop below. ImageDrawPixel(dst, startV, startU, color); // ... but need to be reversed here. Repeated in the main loop below
} }
// We already drew the start point. If we started at startU+0, the line would be crooked and too short. // We already drew the start point. If we started at startU + 0, the line would be crooked and too short
for (int U = startU+1, V = startV; U <= endU; U += 1) for (int u = startU + 1, v = startV; u <= endU; u++)
{ {
if (P >= 0) if (P >= 0)
{ {
V += V_step; // Adjusts whenever we stray too far from the direct line. Details in the linked paper above. v += stepV; // Adjusts whenever we stray too far from the direct line. Details in the linked paper above
P += B; // Remembers that we corrected our path. P += B; // Remembers that we corrected our path
}
else
{
P += A; // Remembers how far we are from the direct line.
}
if (is_x_y_reversed) // Substitutions may be in wrong order for drawing:
{
ImageDrawPixel(dst, U, V, color);
}
else
{
ImageDrawPixel(dst, V, U, color);
} }
else P += A; // Remembers how far we are from the direct line
if (reversedXY) ImageDrawPixel(dst, u, v, color);
else ImageDrawPixel(dst, v, u, color);
} }
} }