195 lines
6.7 KiB
C++
195 lines
6.7 KiB
C++
/*
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This tests the alpha blending function that is used with the antialiased
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fonts:
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Alpha = 0 = 100% background, alpha = 255 = 100% foreground colour
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blendedColor = tft.alphaBlend(alpha, fg_color, bg_color);
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The alphaBlend() function operates on 16 bit colours only
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A test is included where the colours are mapped to 8 bits after blending
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Information on alpha blending is here
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https://en.wikipedia.org/wiki/Alpha_compositing
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Example for library:
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https://github.com/Bodmer/TFT_eSPI
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The sketch has been tested on a 320x240 ILI9341 based TFT, it
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could be adapted for other screen sizes.
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Created by Bodmer 10/2/18
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#########################################################################
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###### DON'T FORGET TO UPDATE THE User_Setup.h FILE IN THE LIBRARY ######
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#########################################################################
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*/
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#include <TFT_eSPI.h> // Include the graphics library
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TFT_eSPI tft = TFT_eSPI(); // Create object "tft"
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// -------------------------------------------------------------------------
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// Setup
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// -------------------------------------------------------------------------
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void setup(void) {
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tft.init();
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tft.setRotation(0);
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tft.fillScreen(TFT_DARKGREY);
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}
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// -------------------------------------------------------------------------
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// Main loop
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// -------------------------------------------------------------------------
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void loop()
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{
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// 16 bit colours (5 bits red, 6 bits green, 5 bits blue)
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// Blend from white to full spectrum
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for (int a = 0; a < 256; a+=2) // Alpha 0 = 100% background, alpha 255 = 100% foreground
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{
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for (int c = 0; c < 192; c++) tft.drawPixel(c, a/2, tft.alphaBlend(a, rainbow(c), TFT_WHITE));
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}
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// Blend from full spectrum to black
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for (int a = 255; a > 2; a-=2)
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{
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for (int c = 0; c < 192; c++) tft.drawPixel(c, 128 + (255-a)/2, tft.alphaBlend(a, rainbow(c), TFT_BLACK));
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}
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// Blend from white to black (32 grey levels)
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for (uint16_t a = 0; a < 255; a++) // Alpha 0 = 100% background, alpha 255 = 100% foreground
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{
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tft.drawFastHLine(192, a, 12, tft.alphaBlend(a, TFT_BLACK, TFT_WHITE));
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tft.drawFastHLine(204, a, 12, tft.alphaBlend(a, TFT_BLACK, TFT_RED));
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tft.drawFastHLine(216, a, 12, tft.alphaBlend(a, TFT_BLACK, TFT_GREEN));
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tft.drawFastHLine(228, a, 12, tft.alphaBlend(a, TFT_BLACK, TFT_BLUE));
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}
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delay(4000);
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// Blend from white to colour (32 grey levels)
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for (uint16_t a = 0; a < 255; a++) // Alpha 0 = 100% background, alpha 255 = 100% foreground
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{
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//tft.drawFastHLine(192, a, 12, tft.alphaBlend(a, TFT_BLACK, TFT_WHITE));
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tft.drawFastHLine(204, a, 12, tft.alphaBlend(a, TFT_RED, TFT_WHITE));
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tft.drawFastHLine(216, a, 12, tft.alphaBlend(a, TFT_GREEN, TFT_WHITE));
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tft.drawFastHLine(228, a, 12, tft.alphaBlend(a, TFT_BLUE, TFT_WHITE));
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}
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delay(4000);
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//*
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// Decrease to 8 bit colour (3 bits red, 3 bits green, 2 bits blue)
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// Blend from white to full spectrum
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for (int a = 0; a < 256; a+=2) // Alpha 0 = 100% background, alpha 255 = 100% foreground
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{
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// Convert blended 16 bit colour to 8 bits to reduce colour resolution, then map back to 16 bits for displaying
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for (int c = 0; c < 192; c++) tft.drawPixel(c, a/2, tft.color8to16(tft.color16to8(tft.alphaBlend(a, rainbow(c), 0xFFFF))));
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}
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// Blend from full spectrum to black
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for (int a = 255; a > 2; a-=2)
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{
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// Convert blended 16 bit colour to 8 bits to reduce colour resolution, then map back to 16 bits for displaying
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for (int c = 0; c < 192; c++) tft.drawPixel(c, 128 + (255-a)/2, tft.color8to16(tft.color16to8(tft.alphaBlend(a, rainbow(c), 0))));
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}
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// Blend from white to black (4 grey levels - it will draw 4 more with a blue tinge due to lower blue bit count)
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// Blend from black to a primary colour
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for (uint16_t a = 0; a < 255; a++) // Alpha 0 = 100% background, alpha 255 = 100% foreground
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{
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tft.drawFastHLine(192, a, 12, tft.color8to16(tft.color16to8(tft.alphaBlend(a, TFT_BLACK, TFT_WHITE))));
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tft.drawFastHLine(204, a, 12, tft.color8to16(tft.color16to8(tft.alphaBlend(a, TFT_BLACK, TFT_RED))));
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tft.drawFastHLine(216, a, 12, tft.color8to16(tft.color16to8(tft.alphaBlend(a, TFT_BLACK, TFT_GREEN))));
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tft.drawFastHLine(228, a, 12, tft.color8to16(tft.color16to8(tft.alphaBlend(a, TFT_BLACK, TFT_BLUE))));
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}
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delay(4000);
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//*/
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/*
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// 16 bit colours (5 bits red, 6 bits green, 5 bits blue)
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for (int a = 0; a < 256; a+=2) // Alpha 0 = 100% background, alpha 255 = 100% foreground
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{
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for (int c = 0; c < 192; c++) tft.drawPixel(c, a/2, tft.alphaBlend(a, rainbow(c), TFT_CYAN));
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}
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// Blend from full spectrum to cyan
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for (int a = 255; a > 2; a-=2)
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{
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for (int c = 0; c < 192; c++) tft.drawPixel(c, 128 + (255-a)/2, tft.alphaBlend(a, rainbow(c), TFT_YELLOW));
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}
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//*/
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/*
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// Blend other colour transitions for test purposes
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for (uint16_t a = 0; a < 255; a++) // Alpha 0 = 100% background, alpha 255 = 100% foreground
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{
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tft.drawFastHLine(192, a, 12, tft.alphaBlend(a, TFT_WHITE, TFT_WHITE)); // Should show as solid white
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tft.drawFastHLine(204, a, 12, tft.alphaBlend(a, TFT_BLACK, TFT_BLACK)); // Should show as solid black
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tft.drawFastHLine(216, a, 12, tft.alphaBlend(a, TFT_YELLOW, TFT_CYAN)); // Brightness should be fairly even
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tft.drawFastHLine(228, a, 12, tft.alphaBlend(a, TFT_CYAN, TFT_MAGENTA));// Brightness should be fairly even
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}
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delay(4000);
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//*/
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}
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// #########################################################################
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// Return a 16 bit rainbow colour
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// #########################################################################
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unsigned int rainbow(byte value)
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{
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// If 'value' is in the range 0-159 it is converted to a spectrum colour
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// from 0 = red through to 127 = blue to 159 = violet
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// Extending the range to 0-191 adds a further violet to red band
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value = value%192;
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byte red = 0; // Red is the top 5 bits of a 16 bit colour value
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byte green = 0; // Green is the middle 6 bits, but only top 5 bits used here
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byte blue = 0; // Blue is the bottom 5 bits
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byte sector = value >> 5;
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byte amplit = value & 0x1F;
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switch (sector)
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{
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case 0:
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red = 0x1F;
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green = amplit; // Green ramps up
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blue = 0;
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break;
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case 1:
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red = 0x1F - amplit; // Red ramps down
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green = 0x1F;
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blue = 0;
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break;
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case 2:
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red = 0;
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green = 0x1F;
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blue = amplit; // Blue ramps up
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break;
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case 3:
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red = 0;
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green = 0x1F - amplit; // Green ramps down
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blue = 0x1F;
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break;
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case 4:
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red = amplit; // Red ramps up
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green = 0;
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blue = 0x1F;
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break;
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case 5:
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red = 0x1F;
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green = 0;
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blue = 0x1F - amplit; // Blue ramps down
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break;
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}
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return red << 11 | green << 6 | blue;
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}
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