GSDP:GAM100/CProcessing/blendMode()

blendMode()

Description

Set the blend mode for subsequent draw calls. See CP_BLEND_MODE for the different blend modes you can set and use.

Parameters

blendMode(CP_BLEND_MODE blendMode)

• blendMode - (CP_BLEND_MODE) The new blend mode to set the program to.

Example

static int currBlendMode = CP_BLEND_ALPHA;
static bool IsCMY = false;
static bool IsAlpha = false;

void DrawBackground()
{
  // draw background with normal alpha blending, half dark, half light
  blendMode(CP_BLEND_ALPHA);
  background(color(50, 50, 50, 255));
  fill(color(200, 200, 200, 255));
  rect(0, 0, canvasWidth * 0.5f, (float)canvasHeight);
}

void DrawCircles()
{
  // setup position, size and color values
  float centerX = canvasWidth * 0.5f;
  float centerY = canvasHeight * 0.5f;
  float circleRadius = 100.0f;
  float offset = 60.0f;
  int bonusColor = 0;
  if (IsCMY == true)
  {
    bonusColor = 255;
  }
  int A = 255;
  if (IsAlpha == true)
  {
    A = 128;
  }
	
  // set current blend mode for circle drawing
  blendMode(currBlendMode);

  // red circle
  fill(color(255, bonusColor, 0, A));
  circle(centerX - offset, centerY - offset, circleRadius);
  // green circle
  fill(color(0, 255, bonusColor, A));
  circle(centerX + offset, centerY - offset, circleRadius);
  // blue circle
  fill(color(bonusColor, 0, 255, A));
  circle(centerX, centerY + offset, circleRadius);
}

void PrintBlendMode()
{
  char* names[] = 
  {
    "CP_BLEND_ALPHA",
    "CP_BLEND_ADD",
    "CP_BLEND_SUBTRACT",
    "CP_BLEND_MULTIPLY",
    "CP_BLEND_MIN",
    "CP_BLEND_MAX"
  };

  blendMode(CP_BLEND_ALPHA);
  fill(color(150, 0, 150, 255));
  text(names[currBlendMode], 20, 50);
}

void HandleInput()
{
  // Press "C" to toggle RGB to CMY circle colors
  if (keyReleased(KEY_C))
  {
    IsCMY = !IsCMY;
  }
  // Press "A" to toggle alpha value to draw semi-transparent circles
  if (keyReleased(KEY_A))
  {
    IsAlpha = !IsAlpha;
  }
  // Press "]" to switch blend mode
  if (keyReleased(KEY_RIGHT_BRACKET))
  {
    ++currBlendMode;
  }
  // Press "[" to switch blend mode
  else if (keyReleased(KEY_LEFT_BRACKET))
  {
    --currBlendMode;
  }

  // keep blend mode within valid range
  currBlendMode = clampInt(currBlendMode, 0, CP_BLEND_MAX);
}

void init()
{
  noStroke();
  textSize(40);
}

void update()
{
  // draw background, half dark, half light
  DrawBackground();

  // draw red, green and blue circles
  DrawCircles();

  // print blend modes to screen
  PrintBlendMode();

  // handle input for changing blend modes
  HandleInput();
}

Related

• Main Page
• CP_BLEND_MODE
• blendMode()