Bad performance - Unoptimized 16-bit color to 24 bit(18 bit) conversion.

[nickshl]

This is not a good way to do such conversion:

uint8_t r = (color & 0xF800) >> 11; uint8_t g = (color & 0x07E0) >> 5; uint8_t b = color & 0x001F; r = (r * 255) / 31; g = (g * 255) / 63; b = (b * 255) / 31;

Much better(2.3 times actually) to do it as such:

// Create 24-bit RGB values from 16 bit uint8_t r = (color & 0xF800) >> 8; // >> 11 << 3 uint8_t g = (color & 0x07E0) >> 3; // >> 5 << 2 uint8_t b = (color & 0x001F) << 3;

But still painfully slow for full screen output

[username7291]

I think he does not maintain it anymore. I found out that too. The thing is for every type of drawing write16BitColor is called. And this color Conversion is done, fillscreen gets 7 times faster if you calculate the color once in Fillrect and only use in the loop writergb color. void ILI9488::writeRGBColor(uint8_t r, uint8_t g, uint8_t b) { spiwrite(r); spiwrite(g); spiwrite(b); }

Usind rgb would better for the user anyway always search the color you want in a internet calculator. But this require to change adafruit_gfx too cause any screen text comes from there.

[username7291]

--global-- uint8_t rgb[3];

void ILI9488::writeRGBColor(uint8_t r, uint8_t g, uint8_t b) { rgb[0]=r; rgb[1]=g; rgb[2]=b; SPI.transfer(&rgb, 3); }

Using one time Color conversion in Rect/Lines and this new Version gives 2-10 times faster (works for Atmega328p only no support for other boards or Software SPI). Thats original Version on a Arduino Pro Mini 8MHZ: Screen fill 82842504 Text 1036360 Lines 14257784 Horiz/Vert Lines 6661184 Rectangles (outline) 3652224 Rectangles (filled) 204570448 Circles (filled) 15878368 Circles (outline) 6078896 Triangles (outline) 3176008 Triangles (filled) 62845464 Rounded rects (outline) 4412440 Rounded rects (filled) 199001768

Thats the optimized Version:

Screen fill 9371376 Text 498496 Lines 9162976 Horiz/Vert Lines 759088 Rectangles (outline) 434904 Rectangles (filled) 22852544 Circles (filled) 2920160 Circles (outline) 3871624 Triangles (outline) 1768400 Triangles (filled) 8477368 Rounded rects (outline) 1372496 Rounded rects (filled) 22776720

You could optimize this more, for fillrect/screenfill for example write more pixels at once if the free Memory allows it.