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apa102: refactor raster functions (#254)

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- rasterImg() now calls raster() instead of duplicating it
- Add a fast path for RGBA
- Add tests for Draw()s called with src and dst offsets supplied
pull/1/head
Ben Lazarus 8 years ago committed by M-A
parent e2aca639ef
commit 70adef3f63
2 changed files with 228 additions and 115 deletions
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215
devices/apa102/apa102.go
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@ -9,6 +9,7 @@ import (
"fmt"
"image"
"image/color"
"image/draw"
"periph.io/x/periph/conn/display"
"periph.io/x/periph/conn/physic"
@ -138,8 +139,7 @@ func (d *Dev) Draw(r image.Rectangle, src image.Image, sp image.Point) error {
if srcR.Empty() {
return nil
}
d.l.init(d.Intensity, d.Temperature)
d.l.rasterImg(d.pixels, r, src, srcR)
d.rasterImg(d.pixels, r, src, srcR)
return d.s.Tx(d.rawBuf, nil)
}
@ -149,9 +149,8 @@ func (d *Dev) Write(pixels []byte) (int, error) {
if len(pixels)%3 != 0 || len(pixels) > len(d.pixels) {
return 0, errors.New("apa102: invalid RGB stream length")
}
d.l.init(d.Intensity, d.Temperature)
// Do not touch header and footer.
d.l.raster(d.pixels, pixels)
d.raster(d.pixels, pixels, false)
err := d.s.Tx(d.rawBuf, nil)
return len(pixels), err
}
@ -170,6 +169,104 @@ func (d *Dev) Halt() error {
return d.s.Tx(d.rawBuf, nil)
}
// raster serializes a buffer of RGB bytes to the APA102 SPI format.
//
// It is expected to be given the part where pixels are, not the header nor
// footer.
//
// dst is in APA102 SPI 32 bits word format. src is in RGB 24 bits word format.
//
// src cannot be longer in pixel count than dst.
//
// if hasAlpha is true, the input buffer is interpreted as having alpha values
// (which are ignored).
func (d *Dev) raster(dst []byte, src []byte, hasAlpha bool) {
pBytes := 3
if hasAlpha {
pBytes = 4
}
length := len(src) / pBytes
if len(dst) < length {
length = len(dst) / pBytes
}
d.l.init(d.Intensity, d.Temperature)
for i := 0; i < length; i++ {
// The response as seen by the human eye is very non-linear. The APA-102
// provides an overall brightness PWM but it is relatively slower and
// results in human visible flicker. On the other hand the minimal color
// (1/255) is still too intense at full brightness, so for very dark color,
// it is worth using the overall brightness PWM. The goal is to use
// brightness!=31 as little as possible.
//
// Global brightness frequency is 580Hz and color frequency at 19.2kHz.
// https://cpldcpu.wordpress.com/2014/08/27/apa102/
// Both are multiplicative, so brightness@50% and color@50% means an
// effective 25% duty cycle but it is not properly distributed, which is
// the main problem.
//
// It is unclear to me if brightness is exactly in 1/31 increment as I don't
// have an oscilloscope to confirm. Same for color in 1/255 increment.
// TODO(maruel): I have one now!
//
// Each channel duty cycle ramps from 100% to 1/(31*255) == 1/7905.
//
// Computes brightness, blue, green, red.
sOff := pBytes * i
dOff := 4 * i
r, g, b := d.l.r[src[sOff]], d.l.g[src[sOff+1]], d.l.b[src[sOff+2]]
m := r | g | b
switch {
case m <= 255:
dst[dOff], dst[dOff+1], dst[dOff+2], dst[dOff+3] = 0xE1, byte(b), byte(g), byte(r)
case m <= 511:
dst[dOff], dst[dOff+1], dst[dOff+2], dst[dOff+3] = 0xE2, byte(b/2), byte(g/2), byte(r/2)
case m <= 1023:
dst[dOff], dst[dOff+1], dst[dOff+2], dst[dOff+3] = 0xE4, byte((b+2)/4), byte((g+2)/4), byte((r+2)/4)
default:
dst[dOff], dst[dOff+1], dst[dOff+2], dst[dOff+3] = 0xFF, byte((b+15)/31), byte((g+15)/31), byte((r+15)/31)
}
}
}
// rasterImg is the generic version of raster that converts an image instead of raw RGB values.
//
// It has 'fast paths' for image.RGBA and image.NRGBA that extract and convert the RGB values
// directly. For other image types, it converts to image.RGBA and then does the same. In all
// cases, alpha values are ignored.
//
// rect specifies where into the output buffer to draw.
//
// srcR specifies what portion of the source image to use.
func (d *Dev) rasterImg(dst []byte, rect image.Rectangle, src image.Image, srcR image.Rectangle) {
// Render directly into the buffer for maximum performance and to keep
// untouched sections intact.
switch im := src.(type) {
case *image.RGBA:
start := im.PixOffset(srcR.Min.X, srcR.Min.Y)
// srcR.Min.Y since the output display has only a single column
end := im.PixOffset(srcR.Max.X, srcR.Min.Y)
// Offset into the output buffer using rect
d.raster(dst[4*rect.Min.X:], im.Pix[start:end], true)
case *image.NRGBA:
// Ignores alpha
start := im.PixOffset(srcR.Min.X, srcR.Min.Y)
// srcR.Min.Y since the output display has only a single column
end := im.PixOffset(srcR.Max.X, srcR.Min.Y)
// Offset into the output buffer using rect
d.raster(dst[4*rect.Min.X:], im.Pix[start:end], true)
default:
// Slow path. Convert to RGBA
b := im.Bounds()
m := image.NewRGBA(image.Rect(0, 0, b.Dx(), b.Dy()))
draw.Draw(m, m.Bounds(), src, b.Min, draw.Src)
start := m.PixOffset(srcR.Min.X, srcR.Min.Y)
// srcR.Min.Y since the output display has only a single column
end := m.PixOffset(srcR.Max.X, srcR.Min.Y)
// Offset into the output buffer using rect
d.raster(dst[4*rect.Min.X:], m.Pix[start:end], true)
}
}
//
// maxOut is the maximum intensity of each channel on a APA102 LED.
@ -248,114 +345,4 @@ func (l *lut) init(i uint8, t uint16) {
}
}
// raster serializes converts a buffer of RGB bytes to the APA102 SPI format.
//
// It is expected to be given the part where pixels are, not the header nor
// footer.
//
// dst is in APA102 SPI 32 bits word format. src is in RGB 24 bits word format.
// maxR, maxG and maxB are the maximum light intensity to use per channel.
//
// src cannot be longer in pixel count than dst.
func (l *lut) raster(dst []byte, src []byte) {
// Whichever is the shortest.
length := len(src) / 3
for i := 0; i < length; i++ {
// Converts a color into the 4 bytes needed to control an APA-102 LED.
//
// The response as seen by the human eye is very non-linear. The APA-102
// provides an overall brightness PWM but it is relatively slower and
// results in human visible flicker. On the other hand the minimal color
// (1/255) is still too intense at full brightness, so for very dark color,
// it is worth using the overall brightness PWM. The goal is to use
// brightness!=31 as little as possible.
//
// Global brightness frequency is 580Hz and color frequency at 19.2kHz.
// https://cpldcpu.wordpress.com/2014/08/27/apa102/
// Both are multiplicative, so brightness@50% and color@50% means an
// effective 25% duty cycle but it is not properly distributed, which is
// the main problem.
//
// It is unclear to me if brightness is exactly in 1/31 increment as I don't
// have an oscilloscope to confirm. Same for color in 1/255 increment.
// TODO(maruel): I have one now!
//
// Each channel duty cycle ramps from 100% to 1/(31*255) == 1/7905.
//
// Computes brighness, blue, green, red.
j := 3 * i
r := l.r[src[j]]
g := l.g[src[j+1]]
b := l.b[src[j+2]]
m := r | g | b
j += i
if m <= 1023 {
if m <= 255 {
dst[j], dst[j+1], dst[j+2], dst[j+3] = byte(0xE0+1), byte(b), byte(g), byte(r)
} else if m <= 511 {
dst[j], dst[j+1], dst[j+2], dst[j+3] = byte(0xE0+2), byte(b>>1), byte(g>>1), byte(r>>1)
} else {
dst[j], dst[j+1], dst[j+2], dst[j+3] = byte(0xE0+4), byte((b+2)>>2), byte((g+2)>>2), byte((r+2)>>2)
}
} else {
// In this case we need to use a ramp of 255-1 even for lower colors.
dst[j], dst[j+1], dst[j+2], dst[j+3] = byte(0xE0+31), byte((b+15)/31), byte((g+15)/31), byte((r+15)/31)
}
}
}
// rasterImg is the generic version of raster.
func (l *lut) rasterImg(dst []byte, rect image.Rectangle, src image.Image, srcR image.Rectangle) {
// Render directly into the buffer for maximum performance and to keep
// untouched sections intact.
deltaX4 := 4 * (rect.Min.X - srcR.Min.X)
if img, ok := src.(*image.NRGBA); ok {
// Fast path for image.NRGBA.
pix := img.Pix[srcR.Min.Y*img.Stride:]
for sX := srcR.Min.X; sX < srcR.Max.X; sX++ {
sX4 := 4 * sX
r := l.r[pix[sX4]]
g := l.g[pix[sX4+1]]
b := l.b[pix[sX4+2]]
m := r | g | b
rX := sX4 + deltaX4
if m <= 1023 {
if m <= 255 {
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+1), byte(b), byte(g), byte(r)
} else if m <= 511 {
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+2), byte(b>>1), byte(g>>1), byte(r>>1)
} else {
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+4), byte((b+2)>>2), byte((g+2)>>2), byte((r+2)>>2)
}
} else {
// In this case we need to use a ramp of 255-1 even for lower colors.
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+31), byte((b+15)/31), byte((g+15)/31), byte((r+15)/31)
}
}
} else {
// Generic version.
for sX := srcR.Min.X; sX < srcR.Max.X; sX++ {
// This causes a memory allocation. There's no way around it.
r16, g16, b16, _ := src.At(sX, srcR.Min.Y).RGBA()
r := l.r[byte(r16>>8)]
g := l.g[byte(g16>>8)]
b := l.b[byte(b16>>8)]
m := r | g | b
rX := sX*4 + deltaX4
if m <= 1023 {
if m <= 255 {
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+1), byte(b), byte(g), byte(r)
} else if m <= 511 {
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+2), byte(b>>1), byte(g>>1), byte(r>>1)
} else {
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+4), byte((b+2)>>2), byte((g+2)>>2), byte((r+2)>>2)
}
} else {
// In this case we need to use a ramp of 255-1 even for lower colors.
dst[rX], dst[rX+1], dst[rX+2], dst[rX+3] = byte(0xE0+31), byte((b+15)/31), byte((g+15)/31), byte((r+15)/31)
}
}
}
}
var _ display.Drawer = &Dev{}

128
devices/apa102/apa102_test.go
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@ -576,7 +576,6 @@ var drawTests = []struct {
img: func() image.Image {
im := image.NewRGBA(image.Rect(0, 0, 16, 1))
for i := 0; i < 16; i++ {
// Test all intensity code paths. Alpha is not ignored in this case.
im.Pix[4*i] = uint8((3 * i) << 2)
im.Pix[4*i+1] = uint8((3*i + 1) << 2)
im.Pix[4*i+2] = uint8((3*i + 2) << 2)
@ -591,6 +590,28 @@ var drawTests = []struct {
Temperature: 5000,
},
},
{
// Just something that doesn't have a fast path
name: "Draw NRGBA64",
img: func() image.Image {
im := image.NewNRGBA64(image.Rect(0, 0, 16, 1))
for i := 0; i < 16; i++ {
im.Set(i, 0, color.NRGBA64{
R: uint16(((3 * i) << 10)),
G: uint16(((3*i + 1) << 10)),
B: uint16(((3*i + 2) << 10)),
A: 0xFFFF,
})
}
return im
}(),
want: expectedi250t5000,
opts: Opts{
NumPixels: 16,
Intensity: 250,
Temperature: 5000,
},
},
}
func TestDraws(t *testing.T) {
@ -606,6 +627,111 @@ func TestDraws(t *testing.T) {
}
}
var offsetDrawWant = []byte{
0x00, 0x00, 0x00, 0x00,
0xE1, 0x89, 0x79, 0x6B,
0xE1, 0x9A, 0x88, 0x75,
0xE1, 0xAD, 0x98, 0x82,
0xE1, 0xC2, 0xAB, 0x92,
0xE1, 0xDA, 0xC0, 0xA4,
0xE1, 0xF5, 0xD9, 0xB9,
0xE2, 0x89, 0x7A, 0x69,
0xE2, 0x9A, 0x8A, 0x76,
0xE2, 0xAC, 0x9B, 0x86,
0xE2, 0xC0, 0xAE, 0x98,
0xE2, 0xD5, 0xC3, 0xAC,
0xE2, 0xED, 0xDA, 0xC2,
0xE4, 0x83, 0x7A, 0x6E,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0xFF,
}
var offsetDrawTests = []struct {
name string
img image.Image
point image.Point
offset image.Rectangle
want []byte
opts Opts
}{
{
name: "Offset Draw NRGBA",
img: func() image.Image {
im := image.NewNRGBA(image.Rect(0, 0, 16, 4))
for x := 0; x < 16; x++ {
for y := 0; y < 4; y++ {
i := (y*16 + x) * 3
im.Set(x, y, color.RGBA{R: uint8(i + 1), G: uint8(i + 2), B: uint8(i + 3), A: 0xFF})
}
}
return im
}(),
point: image.Point{X: 3, Y: 2},
offset: image.Rect(0, 0, 16, 1),
want: offsetDrawWant,
opts: Opts{
NumPixels: 15,
Intensity: 255,
Temperature: 5000,
},
},
{
name: "Both Offset Draw NRGBA",
img: func() image.Image {
im := image.NewNRGBA(image.Rect(0, 0, 16, 4))
for x := 0; x < 16; x++ {
for y := 0; y < 4; y++ {
i := (y*16 + x) * 3
im.Set(x, y, color.RGBA{R: uint8(i + 1), G: uint8(i + 2), B: uint8(i + 3), A: 0xFF})
}
}
return im
}(),
point: image.Point{X: 3, Y: 2},
offset: image.Rect(2, 0, 16, 1),
want: []byte{
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0xE1, 0x89, 0x79, 0x6B,
0xE1, 0x9A, 0x88, 0x75,
0xE1, 0xAD, 0x98, 0x82,
0xE1, 0xC2, 0xAB, 0x92,
0xE1, 0xDA, 0xC0, 0xA4,
0xE1, 0xF5, 0xD9, 0xB9,
0xE2, 0x89, 0x7A, 0x69,
0xE2, 0x9A, 0x8A, 0x76,
0xE2, 0xAC, 0x9B, 0x86,
0xE2, 0xC0, 0xAE, 0x98,
0xE2, 0xD5, 0xC3, 0xAC,
0xE2, 0xED, 0xDA, 0xC2,
0xE4, 0x83, 0x7A, 0x6E,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0xFF, 0xFF,
},
opts: Opts{
NumPixels: 17,
Intensity: 255,
Temperature: 5000,
},
},
}
func TestOffsetDraws(t *testing.T) {
for _, tt := range offsetDrawTests {
buf := bytes.Buffer{}
d, _ := New(spitest.NewRecordRaw(&buf), &tt.opts)
if err := d.Draw(tt.offset, tt.img, tt.point); err != nil {
t.Fatalf("%s: %v", tt.name, err)
}
if !bytes.Equal(buf.Bytes(), tt.want) {
t.Fatalf("%s:\ngot: %#v\nwant: %#v\n", tt.name, buf.Bytes(), tt.want)
}
}
}
func TestHalt(t *testing.T) {
s := spitest.Playback{
Playback: conntest.Playback{

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