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Implemented remaining 7/8 of ImageDrawLine

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The existing code was correct for one octant, it now works for all 8
Added two internal functions, _ImageDrawLineHorizontal and _ImageDrawLineVertical, whithout which it would've been 4 times as much code.
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Alexander Buhl 2021-07-14 00:18:35 +02:00 committed by GitHub
parent 59acb6dbea
commit be83329b2d
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 93 additions and 12 deletions
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105
src/textures.c
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@ -2415,21 +2415,102 @@ void ImageDrawPixelV(Image *dst, Vector2 position, Color color)
ImageDrawPixel(dst, (int)position.x, (int)position.y, color); ImageDrawPixel(dst, (int)position.x, (int)position.y, color);
} }
// Draw line within an image void _ImageDrawLineHorizontal(Image *dst, int startPosX, int startPosY, int endPosX, int endPosY, Color color){
void ImageDrawLine(Image *dst, int startPosX, int startPosY, int endPosX, int endPosY, Color color)
{
int m = 2*(endPosY - startPosY);
int slopeError = m - (endPosX - startPosX);
for (int x = startPosX, y = startPosY; x <= endPosX; x++) int changeInX = (endPosX - startPosX);
int abs_changeInX = changeInX < 0 ? -changeInX : changeInX;
int changeInY = (endPosY - startPosY);
int abs_changeInY = changeInY < 0 ? -changeInY : changeInY;
// we need to go up or down depending (-1 or 1);
int y_directional_unit = changeInY < 0 ? -1 : 1;
int A = 2* abs_changeInY;
int B = A - 2* abs_changeInX;
int P = A - abs_changeInX;
ImageDrawPixel(dst, startPosX, startPosY, color);
for (int x = startPosX+1, y = startPosY; x <= endPosX; x += 1)
{ {
ImageDrawPixel(dst, x, y, color); if (P >= 0)
slopeError += m;
if (slopeError >= 0)
{ {
y++; y += y_directional_unit;
slopeError -= 2*(endPosX - startPosX); P += B;
}
else
{
P += A;
}
ImageDrawPixel(dst, x, y, color);
}
}
void _ImageDrawLineVertical(Image *dst, int startPosX, int startPosY, int endPosX, int endPosY, Color color){
// same code as *Horizontal but with all x and y flipped
int changeInX = (endPosX - startPosX);
int abs_changeInX = changeInX < 0 ? -changeInX : changeInX;
int changeInY = (endPosY - startPosY);
int abs_changeInY = changeInY < 0 ? -changeInY : changeInY;
// we need to go left or right depending (-1 or 1)
int x_directional_unit = changeInX < 0 ? -1 : 1;
int A = 2* abs_changeInX;
int B = A - 2* abs_changeInY;
int P = A - abs_changeInY;
ImageDrawPixel(dst, startPosX, startPosY, color);
for (int y = startPosY+1, x = startPosX; y <= endPosY; y += 1)
{
if (P >= 0)
{
x += x_directional_unit;
P += B;
}
else
{
P += A;
}
ImageDrawPixel(dst, x, y, color);
}
}
// Draw line within an image
void ImageDrawLine (Image *dst, int startPosX, int startPosY, int endPosX, int endPosY, Color color){
// Using Bresenham's algorithm as described in
// Drawing Lines with Pixels - Joshua Scott - March 2012
// https://classic.csunplugged.org/wp-content/uploads/2014/12/Lines.pdf
int changeInX = (endPosX - startPosX);
int abs_changeInX = changeInX < 0 ? -changeInX : changeInX;
int changeInY = (endPosY - startPosY);
int abs_changeInY = changeInY < 0 ? -changeInY : changeInY;
if (abs_changeInY < abs_changeInX)
{
if (changeInX > 0)
{
_ImageDrawLineHorizontal(dst, startPosX, startPosY, endPosX, endPosY, color);
}
else
{
_ImageDrawLineHorizontal(dst, endPosX, endPosY, startPosX, startPosY, color);
}
}
else
{
if (changeInY > 0)
{
_ImageDrawLineVertical(dst, startPosX, startPosY, endPosX, endPosY, color);
}
else
{
_ImageDrawLineVertical(dst, endPosX, endPosY, startPosX, startPosY, color);
} }
} }
} }