Photoshop 如何混合影像，有哪些不同的可用混合模式？

Photoshop 如何合併影像

Photoshop 透過對影像A 的每個像素與其在影像B 中的對應像素執行混合操作來無縫混合影像每個像素由多個通道組成，每個通道代表一種顏色。對於 RGB 像素，這些通道包括紅色、綠色和藍色。

要合併兩個像素，需要使用特定的混合操作組合它們各自的通道。 Photoshop 的混合模式採用以下數學函數：

ChannelBlend_Normal:         ((uint8) A)
ChannelBlend_Lighten:      ((uint8) (B > A) ? B : A)
ChannelBlend_Darken:       ((uint8) (B > A) ? A : B)
ChannelBlend_Multiply:     ((uint8) ((A * B) / 255))
ChannelBlend_Average:      ((uint8) ((A + B) / 2))
ChannelBlend_Add:          ((uint8) min(255, (A + B))))
ChannelBlend_Subtract:     ((uint8) ((A + B < 255) ? 0 : (A + B - 255)))
ChannelBlend_Difference:  ((uint8) abs(A - B))
ChannelBlend_Negation:    ((uint8) (255 - abs(255 - A - B)))
ChannelBlend_Screen:      ((uint8) (255 - (((255 - A) * (255 - B)) >> 8)))
ChannelBlend_Exclusion:   ((uint8) (A + B - 2 * A * B / 255))
ChannelBlend_Overlay:     ((uint8) (B < 128) ? (2 * A * B / 255) : (255 - 2 * (255 - A) * (255 - B) / 255)))
ChannelBlend_SoftLight:   ((uint8) (B < 128) ? (2 * ((A >> 1) + 64)) * ((float) B / 255) : (255 - 2 * (255 - ((A >> 1) + 64)) * (float) (255 - B) / 255))))
ChannelBlend_HardLight:   (ChannelBlend_Overlay(B, A))
ChannelBlend_ColorDodge:  ((uint8) (B == 255) ? B : min(255, ((A << 8 ) / (255 - B)))))
ChannelBlend_ColorBurn:   ((uint8) (B == 0) ? B : max(0, (255 - ((255 - A) << 8 ) / B))))
ChannelBlend_LinearDodge: (ChannelBlend_Add(A, B))
ChannelBlend_LinearBurn:  (ChannelBlend_Subtract(A, B))
ChannelBlend_LinearLight: ((uint8) (B < 128) ? ChannelBlend_LinearBurn(A, (2 * B)) : ChannelBlend_LinearDodge(A, (2 * (B - 128)))))
ChannelBlend_VividLight:  ((uint8) (B < 128) ? ChannelBlend_ColorBurn(A, (2 * B)) : ChannelBlend_ColorDodge(A, (2 * (B - 128)))))
ChannelBlend_PinLight:    ((uint8) (B < 128) ? ChannelBlend_Darken(A, (2 * B)) : ChannelBlend_Lighten(A, (2 * (B - 128)))))
ChannelBlend_HardMix:     ((uint8) ((ChannelBlend_VividLight(A, B) < 128) ? 0 : 255))
ChannelBlend_Reflect:     ((uint8) (B == 255) ? B : min(255, (A * A / (255 - B)))))
ChannelBlend_Glow:        (ChannelBlend_Reflect(B, A))
ChannelBlend_Phoenix:     ((uint8) (min(A, B) - max(A, B) + 255))
ChannelBlend_Alpha:       ((uint8) (O * A + (1 - O) * B))
ChannelBlend_AlphaF:      (ChannelBlend_Alpha(F(A, B), A, O))

混合單一 RGB 像素：

ImageTColorR = ChannelBlend_Glow(ImageAColorR, ImageBColorR);
ImageTColorB = ChannelBlend_Glow(ImageAColorB, ImageBColorB);
ImageTColorG = ChannelBlend_Glow(ImageAColorG, ImageBColorG);

ImageTColor = RGB(ImageTColorR, ImageTColorB, ImageTColorG);

以特定不透明度（例如 50%）混合：

ImageTColorR = ChannelBlend_AlphaF(ImageAColorR, ImageBColorR, Blend_Subtract, 0.5F);

要簡化所有三個通道的混合，可以使用緩衝區宏：

#define ColorBlend_ ## M(T, A, B) (T)[0] = ChannelBlend_ ## M((A)[0], (B)[0]), (T)[1] = ChannelBlend_ ## M((A)[1], (B)[1]), (T)[2] = ChannelBlend_ ## M((A)[2], (B)[2])

產生以下RGB 顏色混合宏：

#define ColorBlend_Normal(T, A, B) ColorBlend_Buffer(T, A, B, Normal)
#define ColorBlend_Lighten(T, A, B) ColorBlend_Buffer(T, A, B, Lighten)
#define ColorBlend_Darken(T, A, B) ColorBlend_Buffer(T, A, B, Darken)
#define ColorBlend_Multiply(T, A, B) ColorBlend_Buffer(T, A, B, Multiply)
#define ColorBlend_Average(T, A, B) ColorBlend_Buffer(T, A, B, Average)
#define ColorBlend_Add(T, A, B) ColorBlend_Buffer(T, A, B, Add)
#define ColorBlend_Subtract(T, A, B) ColorBlend_Buffer(T, A, B, Subtract)
#define ColorBlend_Difference(T, A, B) ColorBlend_Buffer(T, A, B, Difference)
#define ColorBlend_Negation(T, A, B) ColorBlend_Buffer(T, A, B, Negation)
#define ColorBlend_Screen(T, A, B) ColorBlend_Buffer(T, A, B, Screen)
#define ColorBlend_Exclusion(T, A, B) ColorBlend_Buffer(T, A, B, Exclusion)
#define ColorBlend_Overlay(T, A, B) ColorBlend_Buffer(T, A, B, Overlay)
#define ColorBlend_SoftLight(T, A, B) ColorBlend_Buffer(T, A, B, SoftLight)
#define ColorBlend_HardLight(T, A, B) ColorBlend_Buffer(T, A, B, HardLight)
#define ColorBlend_ColorDodge(T, A, B) ColorBlend_Buffer(T, A, B, ColorDodge)
#define ColorBlend_ColorBurn(T, A, B) ColorBlend_Buffer(T, A, B, ColorBurn)
#define ColorBlend_LinearDodge(T, A, B) ColorBlend_Buffer(T, A, B, LinearDodge)
#define ColorBlend_LinearBurn(T, A, B) ColorBlend_Buffer(T, A, B, LinearBurn)
#define ColorBlend_LinearLight(T, A, B) ColorBlend_Buffer(T, A, B, LinearLight)
#define ColorBlend_VividLight(T, A, B) ColorBlend_Buffer(T, A, B, VividLight)
#define ColorBlend_PinLight(T, A, B) ColorBlend_Buffer(T, A, B, PinLight)
#define ColorBlend_HardMix(T, A, B) ColorBlend_Buffer(T, A, B, HardMix)
#define ColorBlend_Reflect(T, A, B) ColorBlend_Buffer(T, A, B, Reflect)
#define ColorBlend_Glow(T, A, B) ColorBlend_Buffer(T, A, B, Glow)
#define ColorBlend_Phoenix(T, A, B) ColorBlend_Buffer(T, A, B, Phoenix)

範例:

ColorBlend_Glow(TargetPtr, ImageAPtr, ImageBPtr);

對於涉及HLS 轉換的混合模式：

#define ColorBlend_Hue(T, A, B) ColorBlend_Hls(T, A, B, HueB, LuminationA, SaturationA)

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