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First results for the new Image widget.

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This commit is contained in:
Oliver 2022-12-25 23:21:11 +01:00
parent cdf60bc79f
commit 8b56f225c5
3 changed files with 418 additions and 31 deletions
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405
image.go
View File

@ -3,6 +3,8 @@ package tview
import (
"image"
"math"
"github.com/gdamore/tcell/v2"
)
// Types of dithering applied to images.
@ -15,17 +17,48 @@ const (
// The number of colors supported by true color terminals (R*G*B = 256*256*256).
const TrueColor = 16777216
// This map describes what each block element looks like. A 1 bit represents a
// pixel that is drawn, a 0 bit represents a pixel that is not drawn. The least
// significant bit is the top left pixel, the most significant bit is the bottom
// right pixel, moving row by row from left to right, top to bottom.
var blockElements = map[rune]uint64{
BlockLowerOneEighthBlock: 0b1111111100000000000000000000000000000000000000000000000000000000,
BlockLowerOneQuarterBlock: 0b1111111111111111000000000000000000000000000000000000000000000000,
BlockLowerThreeEighthsBlock: 0b1111111111111111111111110000000000000000000000000000000000000000,
BlockLowerHalfBlock: 0b1111111111111111111111111111111100000000000000000000000000000000,
BlockLowerFiveEighthsBlock: 0b1111111111111111111111111111111111111111000000000000000000000000,
BlockLowerThreeQuartersBlock: 0b1111111111111111111111111111111111111111111111110000000000000000,
BlockLowerSevenEighthsBlock: 0b1111111111111111111111111111111111111111111111111111111100000000,
BlockLeftSevenEighthsBlock: 0b0111111101111111011111110111111101111111011111110111111101111111,
BlockLeftThreeQuartersBlock: 0b0011111100111111001111110011111100111111001111110011111100111111,
BlockLeftFiveEighthsBlock: 0b0001111100011111000111110001111100011111000111110001111100011111,
BlockLeftHalfBlock: 0b0000111100001111000011110000111100001111000011110000111100001111,
BlockLeftThreeEighthsBlock: 0b0000011100000111000001110000011100000111000001110000011100000111,
BlockLeftOneQuarterBlock: 0b0000001100000011000000110000001100000011000000110000001100000011,
BlockLeftOneEighthBlock: 0b0000000100000001000000010000000100000001000000010000000100000001,
BlockQuadrantLowerLeft: 0b0000111100001111000011110000111100000000000000000000000000000000,
BlockQuadrantLowerRight: 0b1111000011110000111100001111000000000000000000000000000000000000,
BlockQuadrantUpperLeft: 0b0000000000000000000000000000000000001111000011110000111100001111,
BlockQuadrantUpperRight: 0b0000000000000000000000000000000011110000111100001111000011110000,
BlockQuadrantUpperLeftAndLowerRight: 0b1111000011110000111100001111000000001111000011110000111100001111,
}
// pixel represents a character on screen used to draw part of an image.
type pixel struct {
style tcell.Style
element rune // The block element.
}
// Image implements a widget that displays one image. The original image
// (specified with [SetImage]) is resized according to the widget's size (see
// [SetSize]), using the colors available in the terminal (see [SetColors]),
// applying dithering if necessary (see [SetDithering]).
// (specified with [SetImage]) is resized according to the specified size (see
// [SetSize]), using the specified (see [SetColors]), while applying dithering
// if necessary (see [SetDithering]).
//
// Images are approximated by graphical characters in the terminal. The
// resolution is therefore limited by the number of characters that can be drawn
// in the terminal and the colors available in the terminal.
//
// Don't rely on the exact pixels drawn by this widget. The image drawing
// algorithm may change in the future to improve the appearance of the image.
// in the terminal and the colors available in the terminal. The quality of the
// final image also depends on the terminal's font and spacing settings, none of
// which are under the control of this package.
type Image struct {
*Box
@ -56,25 +89,33 @@ type Image struct {
// Horizontal and vertical alignment, one of the "Align" constants.
alignHorizontal, alignVertical int
// The text to be displayed before the image.
label string
// The label style.
labelStyle tcell.Style
// The screen width of the label area. A value of 0 means use the width of
// the label text.
labelWidth int
// The actual image size (in cells) when it was drawn the last time.
lastWidth, lastHeight int
// The actual image (in cells) when it was drawn the last time. The size of
// this slice is 4 * lastWidth * lastHeight (with a factor of 4 because we
// can draw four pixels per cell), indexed by y*lastWidth*2 + x. Each pixel
// is an RGB value (0-255).
pixels [][3]int
// this slice is lastWidth * lastHeight, indexed by y*lastWidth + x.
pixels []pixel
}
// NewImage returns a new image widget with an empty image (use [SetImage] to
// specify the image to be displayed). The image will use the widget's entire
// available space. The dithering algorithm is set to Floyd-Steinberg dithering.
// The terminal's cell aspect ratio is set to 1.
// The terminal's cell aspect ratio is set to 0.5.
func NewImage() *Image {
return &Image{
Box: NewBox(),
dithering: ImageDitheringFloydSteinberg,
aspectRatio: 1,
aspectRatio: 0.5,
alignHorizontal: AlignCenter,
alignVertical: AlignCenter,
}
@ -131,7 +172,7 @@ func (i *Image) SetBackgroundColor(r, g, b int8) *Image {
}
// SetAspectRatio sets the width of a terminal's cell divided by its height.
// You may change the default of 1 if your terminal uses a different aspect
// You may change the default of 0.5 if your terminal uses a different aspect
// ratio. This is used to calculate the size of the image if one of the sizes
// is 0. The function will panic if the aspect ratio is 0 or less.
func (i *Image) SetAspectRatio(aspectRatio float64) *Image {
@ -153,6 +194,35 @@ func (i *Image) SetAlign(vertical, horizontal int) *Image {
return i
}
// SetLabel sets the text to be displayed before the image.
func (i *Image) SetLabel(label string) *Image {
i.label = label
return i
}
// GetLabel returns the text to be displayed before the image.
func (i *Image) GetLabel() string {
return i.label
}
// SetLabelWidth sets the screen width of the label. A value of 0 will cause the
// primitive to use the width of the label string.
func (i *Image) SetLabelWidth(width int) *Image {
i.labelWidth = width
return i
}
// SetLabelStyle sets the style of the label.
func (i *Image) SetLabelStyle(style tcell.Style) *Image {
i.labelStyle = style
return i
}
// GetLabelStyle returns the style of the label.
func (i *Image) GetLabelStyle() tcell.Style {
return i.labelStyle
}
// render re-populates the [Image.pixels] slice besed on the current settings,
// if [Image.lastWidth] and [Image.lastHeight] don't match the current image's
// size. It also sets the new image size in these two variables.
@ -171,6 +241,15 @@ func (i *Image) render() {
}
width, height := i.width, i.height
_, _, innerWidth, innerHeight := i.GetInnerRect()
if i.labelWidth > 0 {
innerWidth -= i.labelWidth
} else {
innerWidth -= TaggedStringWidth(i.label)
}
if innerWidth <= 0 {
i.pixels = nil
return
}
if width == 0 && height == 0 {
// Use all available space.
width, height = innerWidth, innerHeight
@ -206,14 +285,20 @@ func (i *Image) render() {
}
i.lastWidth, i.lastHeight = width, height // This could still be larger than the available space but that's ok for now.
// Generate the initial pixels by resizing the image.
i.resize()
// Generate the initial pixels by resizing the image (8x8 per cell).
pixels := i.resize()
// Turn them into block elements with background/foreground colors.
i.stamp(pixels)
}
// resize resizes the image to the current size and stores the result in
// [Image.pixels]. It is assumed that [Image.lastWidth] and [Image.lastHeight]
// are positive values.
func (i *Image) resize() {
// resize resizes the image to the current size and returns the result as a
// slice of pixels. It is assumed that [Image.lastWidth] (w) and
// [Image.lastHeight] (h) are positive, non-zero values, and the slice has a
// size of 64*w*h, with each pixel being represented by 3 float64 values in the
// range of 0-1. The factor of 64 is due to the fact that we calculate 8x8
// pixels per cell.
func (i *Image) resize() [][3]float64 {
// Because most of the time, we will be downsizing the image, we don't even
// attempt to do any fancy interpolation. For each target pixel, we
// calculate a weighted average of the source pixels using their coverage
@ -221,14 +306,14 @@ func (i *Image) resize() {
bounds := i.image.Bounds()
srcWidth, srcHeight := bounds.Dx(), bounds.Dy()
tgtWidth, tgtHeight := i.lastWidth*2, i.lastHeight*2
coverageWidth, coverageHeight := float64(srcWidth)/float64(tgtWidth), float64(srcHeight)/float64(tgtHeight)
i.pixels = make([][3]int, tgtWidth*tgtHeight)
tgtWidth, tgtHeight := i.lastWidth*8, i.lastHeight*8
coverageWidth, coverageHeight := float64(tgtWidth)/float64(srcWidth), float64(tgtHeight)/float64(srcHeight)
pixels := make([][3]float64, tgtWidth*tgtHeight)
weights := make([]float64, tgtWidth*tgtHeight)
for srcY := bounds.Min.Y; srcY < bounds.Max.Y; srcY++ {
for srcX := bounds.Min.X; srcX < bounds.Max.X; srcX++ {
r32, g32, b32, _ := i.image.At(srcX, srcY).RGBA()
r, g, b := int(r32>>8), int(g32>>8), int(b32>>8)
r, g, b := float64(r32)/0xffff, float64(g32)/0xffff, float64(b32)/0xffff
// Iterate over all target pixels. Outer loop is Y.
startY := float64(srcY-bounds.Min.Y) * coverageHeight
@ -258,10 +343,11 @@ func (i *Image) resize() {
// Add a weighted contribution to the target pixel.
index := tgtY*tgtWidth + tgtX
i.pixels[index][0] += r
i.pixels[index][1] += g
i.pixels[index][2] += b
weights[index] += coverageX * coverageY
coverage := coverageX * coverageY
pixels[index][0] += r * coverage
pixels[index][1] += g * coverage
pixels[index][2] += b * coverage
weights[index] += coverage
}
}
}
@ -270,9 +356,266 @@ func (i *Image) resize() {
// Normalize the pixels.
for index, weight := range weights {
if weight > 0 {
i.pixels[index][0] = int(float64(i.pixels[index][0]) / weight)
i.pixels[index][1] = int(float64(i.pixels[index][1]) / weight)
i.pixels[index][2] = int(float64(i.pixels[index][2]) / weight)
pixels[index][0] /= weight
pixels[index][1] /= weight
pixels[index][2] /= weight
}
}
return pixels
}
// stamp takes the pixels generated by [Image.resize] and populates the
// [Image.pixels] slice accordingly.
func (i *Image) stamp(resized [][3]float64) {
// For each 8x8 pixel block, we find the best block element to represent it,
// given the available colors.
i.pixels = make([]pixel, i.lastWidth*i.lastHeight)
colors := i.colors
if colors == 0 {
colors = availableColors
}
for row := 0; row < i.lastHeight; row++ {
for col := 0; col < i.lastWidth; col++ {
// Calculate an error for each potential block element + color. Keep
// the one with the lowest error.
minMSE := math.MaxFloat64 // Mean squared error.
for element, bits := range blockElements {
// Calculate the average color for the pixels covered by the set
// bits and unset bits.
var (
bg, fg [3]float64
setBits float64
bit uint64 = 1
)
for y := 0; y < 8; y++ {
for x := 0; x < 8; x++ {
index := (row*8+y)*i.lastWidth*8 + (col*8 + x)
if bits&bit != 0 {
fg[0] += resized[index][0]
fg[1] += resized[index][1]
fg[2] += resized[index][2]
setBits++
} else {
bg[0] += resized[index][0]
bg[1] += resized[index][1]
bg[2] += resized[index][2]
}
bit <<= 1
}
}
fg[0] /= setBits
fg[1] /= setBits
fg[2] /= setBits
bg[0] /= 64 - setBits
bg[1] /= 64 - setBits
bg[2] /= 64 - setBits
// Quantize to the nearest acceptable color.
for _, color := range []*[3]float64{&fg, &bg} {
if colors <= 2 {
// Monochrome. The following weights correspond better
// to human perception than the arithmetic mean.
gray := 0.299*color[0] + 0.587*color[1] + 0.114*color[2]
if gray < 0.5 {
*color = [3]float64{0, 0, 0}
} else {
*color = [3]float64{1, 1, 1}
}
} else {
for index, ch := range color {
switch {
case colors <= 8:
// Colors vary wildly for each terminal. Expect
// suboptimal results.
if ch < 0.5 {
color[index] = 0
} else {
color[index] = 1
}
case colors <= 256:
color[index] = math.Round(ch*6) / 6
}
}
}
}
// Calculate the error.
var mse float64
bit = 1
for y := 0; y < 8; y++ {
for x := 0; x < 8; x++ {
index := (row*8+y)*i.lastWidth*8 + (col*8 + x)
for ch := 0; ch < 3; ch++ {
err := resized[index][ch]
if bits&bit != 0 {
err -= fg[ch]
} else {
err -= bg[ch]
}
mse += err * err
}
bit <<= 1
}
}
// Do we have a better match?
if mse < minMSE {
// Yes. Save it.
minMSE = mse
index := row*i.lastWidth + col
i.pixels[index].element = element
i.pixels[index].style = tcell.StyleDefault.
Foreground(tcell.NewRGBColor(int32(math.Min(255, fg[0]*255)), int32(math.Min(255, fg[1]*255)), int32(math.Min(255, fg[2]*255)))).
Background(tcell.NewRGBColor(int32(math.Min(255, bg[0]*255)), int32(math.Min(255, bg[1]*255)), int32(math.Min(255, bg[2]*255))))
}
}
// Check if there is a shade block which results in a smaller error.
// What's the overall average color?
var avg [3]float64
for y := 0; y < 8; y++ {
for x := 0; x < 8; x++ {
index := (row*8+y)*i.lastWidth*8 + (col*8 + x)
for ch := 0; ch < 3; ch++ {
avg[ch] += resized[index][ch] / 64
}
}
}
// Quantize and choose shade element.
element := BlockFullBlock
var fg, bg tcell.Color
shades := []rune{' ', BlockLightShade, BlockMediumShade, BlockDarkShade, BlockFullBlock}
if colors <= 2 {
// Monochrome.
gray := 0.299*avg[0] + 0.587*avg[1] + 0.114*avg[2] // See above for details.
shade := int(math.Round(gray * 4))
element = shades[shade]
for ch := 0; ch < 3; ch++ {
avg[ch] = float64(shade) / 4
}
bg = tcell.ColorBlack
fg = tcell.ColorWhite
} else if colors > 256 {
// True color.
fg = tcell.NewRGBColor(int32(math.Min(255, avg[0]*255)), int32(math.Min(255, avg[1]*255)), int32(math.Min(255, avg[2]*255)))
bg = fg
} else {
// 8 or 256 colors.
steps := 1.0
if colors > 8 {
steps = 6.0
}
var (
lo, hi, pos [3]float64
shade float64
)
for ch := 0; ch < 3; ch++ {
lo[ch] = math.Floor(avg[ch]*steps) / steps
hi[ch] = math.Ceil(avg[ch]*steps) / steps
if r := hi[ch] - lo[ch]; r > 0 {
pos[ch] = (avg[ch] - lo[ch]) / r
if math.Abs(pos[ch]-0.5) < math.Abs(shade-0.5) {
shade = pos[ch]
}
}
}
shade = math.Round(shade * 4)
element = shades[int(shade)]
shade /= 4
for ch := 0; ch < 3; ch++ { // Find the closest channel value.
best := math.Abs(avg[ch] - (lo[ch] + (hi[ch]-lo[ch])*shade)) // Start shade from lo to hi.
if value := math.Abs(avg[ch] - (hi[ch] - (hi[ch]-lo[ch])*shade)); value < best {
best = value // Swap lo and hi.
lo[ch], hi[ch] = hi[ch], lo[ch]
}
if value := math.Abs(avg[ch] - lo[ch]); value < best {
best = value // Use lo.
hi[ch] = lo[ch]
}
if value := math.Abs(avg[ch] - hi[ch]); value < best {
lo[ch] = hi[ch] // Use hi.
}
avg[ch] = lo[ch] + (hi[ch]-lo[ch])*shade // Quantize.
}
bg = tcell.NewRGBColor(int32(math.Min(255, lo[0]*255)), int32(math.Min(255, lo[1]*255)), int32(math.Min(255, lo[2]*255)))
fg = tcell.NewRGBColor(int32(math.Min(255, hi[0]*255)), int32(math.Min(255, hi[1]*255)), int32(math.Min(255, hi[2]*255)))
}
// Calculate the error.
var mse float64
for y := 0; y < 8; y++ {
for x := 0; x < 8; x++ {
index := (row*8+y)*i.lastWidth*8 + (col*8 + x)
for ch := 0; ch < 3; ch++ {
err := resized[index][ch] - avg[ch]
mse += err * err
}
}
}
// Is this shade element better than the block element?
if mse < minMSE {
// Yes. Save it.
index := row*i.lastWidth + col
i.pixels[index].element = element
i.pixels[index].style = tcell.StyleDefault.Foreground(fg).Background(bg)
}
}
}
}
// Draw draws this primitive onto the screen.
func (i *Image) Draw(screen tcell.Screen) {
i.DrawForSubclass(screen, i)
// Regenerate image if necessary.
i.render()
// Draw label.
viewX, viewY, viewWidth, viewHeight := i.GetInnerRect()
_, labelBg, _ := i.labelStyle.Decompose()
if i.labelWidth > 0 {
labelWidth := i.labelWidth
if labelWidth > viewWidth {
labelWidth = viewWidth
}
printWithStyle(screen, i.label, viewX, viewY, 0, labelWidth, AlignLeft, i.labelStyle, labelBg == tcell.ColorDefault)
viewX += labelWidth
viewWidth -= labelWidth
} else {
_, drawnWidth, _, _ := printWithStyle(screen, i.label, viewX, viewY, 0, viewWidth, AlignLeft, i.labelStyle, labelBg == tcell.ColorDefault)
viewX += drawnWidth
viewWidth -= drawnWidth
}
// Determine image placement.
x, y, width, height := viewX, viewY, i.lastWidth, i.lastHeight
if i.alignHorizontal == AlignCenter {
x += (viewWidth - width) / 2
} else if i.alignHorizontal == AlignRight {
x += viewWidth - width
}
if i.alignVertical == AlignCenter {
y += (viewHeight - height) / 2
} else if i.alignVertical == AlignBottom {
y += viewHeight - height
}
// Draw the image.
for row := 0; row < height; row++ {
if y+row < viewY || y+row >= viewY+viewHeight {
continue
}
for col := 0; col < width; col++ {
if x+col < viewX || x+col >= viewX+viewWidth {
continue
}
index := row*width + col
screen.SetContent(x+col, y+row, i.pixels[index].element, nil, i.pixels[index].style)
}
}
}

34
semigraphics.go
View File

@ -139,6 +139,40 @@ const (
BoxDrawingsLightUpAndHeavyDown rune = '\u257d' // ╽
BoxDrawingsHeavyLeftAndLightRight rune = '\u257e' // ╾
BoxDrawingsHeavyUpAndLightDown rune = '\u257f' // ╿
// Block Elements.
BlockUpperHalfBlock rune = '\u2580' // ▀
BlockLowerOneEighthBlock rune = '\u2581' // ▁
BlockLowerOneQuarterBlock rune = '\u2582' // ▂
BlockLowerThreeEighthsBlock rune = '\u2583' // ▃
BlockLowerHalfBlock rune = '\u2584' // ▄
BlockLowerFiveEighthsBlock rune = '\u2585' // ▅
BlockLowerThreeQuartersBlock rune = '\u2586' // ▆
BlockLowerSevenEighthsBlock rune = '\u2587' // ▇
BlockFullBlock rune = '\u2588' // █
BlockLeftSevenEighthsBlock rune = '\u2589' // ▉
BlockLeftThreeQuartersBlock rune = '\u258A' // ▊
BlockLeftFiveEighthsBlock rune = '\u258B' // ▋
BlockLeftHalfBlock rune = '\u258C' // ▌
BlockLeftThreeEighthsBlock rune = '\u258D' // ▍
BlockLeftOneQuarterBlock rune = '\u258E' // ▎
BlockLeftOneEighthBlock rune = '\u258F' // ▏
BlockRightHalfBlock rune = '\u2590' // ▐
BlockLightShade rune = '\u2591' // ░
BlockMediumShade rune = '\u2592' // ▒
BlockDarkShade rune = '\u2593' // ▓
BlockUpperOneEighthBlock rune = '\u2594' // ▔
BlockRightOneEighthBlock rune = '\u2595' // ▕
BlockQuadrantLowerLeft rune = '\u2596' // ▖
BlockQuadrantLowerRight rune = '\u2597' // ▗
BlockQuadrantUpperLeft rune = '\u2598' // ▘
BlockQuadrantUpperLeftAndLowerLeftAndLowerRight rune = '\u2599' // ▙
BlockQuadrantUpperLeftAndLowerRight rune = '\u259A' // ▚
BlockQuadrantUpperLeftAndUpperRightAndLowerLeft rune = '\u259B' // ▛
BlockQuadrantUpperLeftAndUpperRightAndLowerRight rune = '\u259C' // ▜
BlockQuadrantUpperRight rune = '\u259D' // ▝
BlockQuadrantUpperRightAndLowerLeft rune = '\u259E' // ▞
BlockQuadrantUpperRightAndLowerLeftAndLowerRight rune = '\u259F' // ▟
)
// SemigraphicJoints is a map for joining semigraphic (or otherwise) runes.

10
util.go
View File

@ -2,6 +2,7 @@ package tview
import (
"math"
"os"
"regexp"
"sort"
"strconv"
@ -36,6 +37,9 @@ const (
colorFlagPos = 5
)
// The number of colors available in the terminal.
var availableColors = 256
// Predefined InputField acceptance functions.
var (
// InputFieldInteger accepts integers.
@ -73,6 +77,12 @@ func init() {
return len([]rune(text)) <= maxLength
}
}
// Determine the number of colors available in the terminal.
info, err := tcell.LookupTerminfo(os.Getenv("TERM"))
if err == nil {
availableColors = info.Colors
}
}
// styleFromTag takes the given style, defined by a foreground color (fgColor),