94 lines
2.3 KiB
Go
94 lines
2.3 KiB
Go
package screen
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import (
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"image"
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"image/color"
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)
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const (
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loResPixelWidth = charWidth * 2
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doubleLoResPixelWidth = charWidth
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loResPixelHeight = charHeight / 2
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)
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func getColorPatterns(light color.Color) [16][16]color.Color {
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/*
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For each lores pixel we have to fill 14 half mono pixels with
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the 4 bits of the color repeated. We will need to shift by 2 bits
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on the odd columns. Lets prepare 14+2 values for each color.
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*/
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var data [16][16]color.Color
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for ci := 0; ci < 16; ci++ {
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for cb := uint8(0); cb < 4; cb++ {
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bit := (ci >> cb) & 1
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var colour color.Color
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if bit == 0 {
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colour = color.Black
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} else {
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colour = light
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}
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for i := uint8(0); i < 4; i++ {
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data[ci][cb+4*i] = colour
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}
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}
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}
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return data
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}
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func snapshotLoRes(vs VideoSource, isSecondPage bool, light color.Color) *image.RGBA {
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data := getTextFromMemory(vs, isSecondPage, false)
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return renderGr(data, false /*isMeres*/, light)
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}
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func snapshotMeRes(vs VideoSource, isSecondPage bool, light color.Color) *image.RGBA {
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data := getText80FromMemory(vs, isSecondPage)
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return renderGr(data, true /*isMeres*/, light)
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}
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func renderGr(data []uint8, isDoubleResMode bool, light color.Color) *image.RGBA {
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grLines := textLines * 2
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columns := len(data) / textLines
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pixelWidth := loResPixelWidth
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if isDoubleResMode {
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pixelWidth = doubleLoResPixelWidth
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}
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size := image.Rect(0, 0, columns*pixelWidth, grLines*loResPixelHeight)
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img := image.NewRGBA(size)
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patterns := getColorPatterns(light)
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for l := 0; l < grLines; l++ {
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for c := 0; c < columns; c++ {
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char := data[(l/2)*columns+c]
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grPixel := char >> 4
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if l%2 == 0 {
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grPixel = char & 0xf
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}
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// We place pixelWidth mono pixels per graphic pixel.
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// The groups of 4 mono pixels need to be aligned with an offset to get plain surfaces
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offset := (c * pixelWidth) % 4
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if isDoubleResMode && ((c % 2) == 0) {
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// See "Understanding the Apple II", page 8-44
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// Even blocks color are rotated left one bit
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offset = offset + 3 // Equivalent to -1
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}
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// Insert the pixelWidth pixels required
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for i := 0; i < pixelWidth; i++ {
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v := patterns[grPixel][i+offset]
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// Repeat the same color for 4 lines
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for r := 0; r < loResPixelHeight; r++ {
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img.Set(c*pixelWidth+i, l*4+r, v)
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}
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}
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}
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}
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return img
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}
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