Graphics Functions
Talkback #2 written by Zip on 2004-06-12.
int GetMaskByColour(int gmbc_col, int gmbc_image)
// Creates a mask of an image, magenta background, black where specified colour is
// Pass: the colour to create mask from; image handle
// Return: the handle to the mask created
// Assumes: you have global: int x, y; Rename and declare locally if you like
{
int gmbc_h = ImageHeight(gmbc_image); // Height of passed image
int gmbc_w = ImageWidth(gmbc_image); // Width of passed image
// Gets pointer to new image of same dimensions
int gmbc_handle = NewImage(gmbc_w, gmbc_h);
for (y = 0; y < gmbc_h; y++) // Scan through all y pixels
{
for (x = 0; x < gmbc_w; x++) // Scan through all x pixels
{
// If this pixel matches the set colour
if (GetPixel(x, y, gmbc_image) == gmbc_col)
{
// Put a black pixel in the mask
SetPixel(x, y, 0, gmbc_handle);
}
else // Otherwise put a magenta pixel in the mask
{
SetPixel(x, y, 16711935, gmbc_handle);
}
}
}
return gmbc_handle; // Return the pointer to the mask
}
Use if you frequently need to change a colour in an image. The function itself is slow, but it only needs to be called once per image, per colour. Whenever you need a different colour, Blit() the original image, then Silhouette() the mask over it with whatever colour you desire.
Example: Add in the code above and the Wait() code, and put the image in the same directory
int x, y;
void autoexec()
{
int r,g,b; // To store colour values
int vimg = LoadImage("v3.gif"); // Loads image of v3 logo
// Creates mask of white values
int vmask = GetMaskByColour(RGB(255,255,255), vimg);
while (!b3) // If espace is not pressed
{
r += 1; // Cycle through red values...
g += 2; // ...and green...
b += 4; // ...and blue
Blit(0, 0, vimg, screen); // Puts the image in the screen buffer
// Blits coloured mask over the top
Silhouette(0, 0, RGB(r,g,b), vmask, screen);
ShowPage(); // Displays the buffer on the screen
Wait(5); // Wait 5 timer ticks
}
FreeImage(vimg); // Remove image from memory
FreeImage(vmask); // Ditto
exit("Bye!");
}
Talkback #1 written by Zip on 2004-06-12.
void SwapColours(int sc_col_out, int sc_col_in, int sc_image)
// Changes all of one colour value in an image to another colour
// Pass: the colour to replace; the colour to insert; image handle
// Assumes: you have global: int x, y; Rename and declare locally if you like
{
int sc_h = ImageHeight(sc_image); // Height of passed image
int sc_w = ImageWidth(sc_image); // Width of passed image
for (y = 0; y < sc_h; y++) // Scan through all y pixels
{
for (x = 0; x < sc_w; x++) // Scan through all x pixels
{
// If this pixel matches the old colour
if (GetPixel(x, y, sc_image) == sc_col_out)
// Set the pixel to the new colour
SetPixel(x, y, sc_col_in, sc_image);
}
}
}
Use for infrequent changing of one colour. As this is a slow function (and increasingly so with larger images) you only want to be calling it when you need to. To deal with more frequent changes use GetMaskByColour() and blit the mask as a silhouette over the original image.
Example: Add in the code above, and put the image in the same directory
int x, y;
void autoexec()
{
int test = LoadImage("v3.gif"); // Loads image of v3 logo
Blit(0, 0, test, screen); // Puts the image in the screen buffer
SwapColours(RGB(255,255,255), RGB(0,255,0), test); // Change white to green
Blit(100, 0, test, screen); // Puts image on screen with all white now green
ShowPage(); // Displays the buffer on the screen
FreeImage(test); // Remove image from memory
while (!b3) // If espace is not pressed
{
UpdateControls(); // Check inputs
}
exit("Bye!");
}
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Verge-rpg.com is a member of the lunarnet irc network, and would like to take this opportunity to remind you that regardless how babies taste, it is wrong to eat them.