TWI780634B - Image calibration method of image system - Google Patents
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本發明關於影像處理,特別是一種維持色外貌一致性的影像系統之影像校正方法。 The present invention relates to image processing, in particular to an image correction method for an image system that maintains color appearance consistency.
投影機係為一種光學裝置,用以將影像投影至螢幕上。習知技術的投影機的投影影像會受到環境光影響,導致影像色彩在環境光下與暗房中的色外貌表現不一致。 A projector is an optical device used to project images onto a screen. The projected image of the conventional projector is affected by the ambient light, causing the image color to be inconsistent with the color appearance in the darkroom under the ambient light.
目前投影機多針對投影機的硬體架構,而少有針對使用者所處環境的視覺感受進行校正,因此需要一種投影機,能於不同環境光下維持色外貌一致性,以使使用者的視覺感受不受環境光源影響。 At present, most projectors are aimed at the hardware structure of the projector, but seldom corrected for the visual experience of the user's environment. Therefore, there is a need for a projector that can maintain the consistency of color appearance under different ambient lights so that the user's Visual perception is not affected by ambient light sources.
本發明實施例提供一種影像系統之影像校正方法。影像系統包含投影裝置、色彩感測器及處理器。影像校正方法包含於環境光下,設置該投影裝置以使用一第一色域將一測試影像投影至投影表面,該測試影像包含黑色、白色及至少一特定色,於環境光下,色彩感測器測量表面上之測試影像的黑色之一組環境光測量值、白色之一組環境光測量值及至少一特定色之至少一組環境光測量值,處理器依據黑色之該組環境光測量值、白色之該組環境光測量值、至少一特定色之至少一組環境光測量值、環境光的可適性區域亮度、環境光背景亮度及一組環境光環繞參數來產生黑色之一組色外貌表示值、白色之一組色 外貌表示值及至少一特定色之至少一組色外貌表示值,於暗室下,投影裝置將測試影像投影至表面,於暗室下,色彩感測器測量表面上之測試影像的白色之一組暗室測量值及黑色之一組暗室測量值,若環繞比率小於一預定臨界值,處理器依據至少一特定色之至少一組色外貌表示值、白色之該組暗室測量值、暗室的可適性區域亮度、暗室背景亮度及一組暗室環繞參數來產生至少一特定色之至少一組目標值,處理器依據至少一特定色之至少一組目標值將投影裝置設置至第二色域,第一色域及第二色域不同,處理器將原始影像中之畫素的一組色值依據第二色域進行色域轉換以產生一組轉換色值,組轉換色值包含第一顏色成分值、第二顏色成分值及第三顏色成分值,處理器將黑色之該組色外貌表示值中之亮度加入第一顏色成分值、第二顏色成分值及第三顏色成分值分別產生調整後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值;及於暗室下,投影裝置投影調整後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值。 An embodiment of the present invention provides an image correction method of an image system. The image system includes a projection device, a color sensor and a processor. The image correction method includes setting the projection device to project a test image onto the projection surface using a first color gamut under ambient light, the test image includes black, white and at least one specific color, and under the ambient light, the color sensing A set of ambient light measurements for black, a set of ambient light measurements for white, and at least one set of ambient light measurements for at least one specific color of the test image on the surface of the device, the processor based on the set of ambient light measurements for black , the set of ambient light measurements for white, at least one set of ambient light measurements for at least one specific color, the ambient light adaptability area luminance, the ambient light background luminance, and a set of ambient light surround parameters to generate a set of color appearances for black Indicates a value, a set of colors of white Appearance representation value and at least one set of color appearance representation values of at least one specific color. In a dark room, a projection device projects a test image onto a surface. Under a dark room, a color sensor measures a set of whiteness of the test image on the surface. A set of darkroom measurements of measured values and black, if the surround ratio is less than a predetermined threshold value, the processor based on at least one set of color appearance representation values of at least one specific color, the set of darkroom measurements of white, and the adaptive area brightness of the darkroom , dark room background brightness and a set of dark room surrounding parameters to generate at least one set of target values of at least one specific color, the processor sets the projection device to the second color gamut and the first color gamut according to at least one set of target values of at least one specific color Different from the second color gamut, the processor converts a set of color values of pixels in the original image according to the second color gamut to generate a set of converted color values. The set of converted color values includes the first color component value, the second The second color component value and the third color component value, the processor adds the brightness of the black color appearance representation value to the first color component value, the second color component value and the third color component value to generate the adjusted first color component value respectively. The color component value, the adjusted second color component value and the adjusted third color component value; and in a dark room, the projection device projects the adjusted first color component value, the adjusted second color component value and the adjusted The value of the third color component.
本發明實施例提供另一種影像系統之影像校正方法。影像系統包含投影裝置、色彩感測器及處理器。影像校正方法包含於環境光下,設置投影裝置以使用第一色域以將測試影像投影至表面,測試影像包含黑色、白色,於環境光下,色彩感測器測量表面上之測試影像的黑色之該組環境光測量值及白色之該組環境光測量值,處理器依據黑色之該組環境光測量值、白色之該組環境光測量值、環境光的可適性區域亮度、環境光背景亮度及一組環境光環繞參數來產生黑色之一組色外貌表示值,處理器將原始影像中之畫素的一組色值依據第二色域進行色域轉換以產生一組轉換色值,組轉換色值包含第一顏色成分值、第二顏色成分值及第三顏色成分值,處理器將黑色之組色外貌表示值中之亮度加入第一顏色成分值、第二顏色成分值及第三顏色成分值以分別產生調整 後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值,及於暗室下,投影裝置投影調整後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值。若第一顏色成分值大於第二顏色成分值、第三顏色成分值及校正臨界值,調整後之第一顏色成分值和第一顏色成分值成正相關,調整後之第二顏色成分值和第二顏色成分值成負相關,及調整後之第三顏色成分值和第三顏色成分值成負相關。若第一顏色成分值大於第二顏色成分值及第三顏色成分值,但小於校正臨界值時,調整後之第一顏色成分值和第一顏色成分值之伽馬校正值成正相關,調整後之第二顏色成分值和第二顏色成分值之伽馬校正值成負相關,及調整後之第三顏色成分值和第三顏色成分值之伽馬校正值成負相關。 An embodiment of the present invention provides another image correction method for an image system. The image system includes a projection device, a color sensor and a processor. The image correction method includes setting the projection device to use the first color gamut to project a test image onto the surface under ambient light. The test image includes black and white. Under ambient light, the color sensor measures the black of the test image on the surface The group of measured values of ambient light for white and the group of measured values of ambient light for white, the processor bases the group of measured values of ambient light for black, the group of measured values of ambient light for white, the brightness of the adaptable area of ambient light, and the brightness of the background of ambient light and a set of ambient light surround parameters to generate a set of color appearance representation values for black. The processor converts a set of color values of pixels in the original image according to the second color gamut to generate a set of transformed color values. The converted color value includes the first color component value, the second color component value and the third color component value. Color component values to generate adjustments separately The adjusted first color component value, the adjusted second color component value, and the adjusted third color component value, and in a dark room, the projection device projects the adjusted first color component value and the adjusted second color component value value and the adjusted value of the third color component. If the first color component value is greater than the second color component value, the third color component value and the correction threshold value, the adjusted first color component value and the first color component value are positively correlated, and the adjusted second color component value and the first color component value are positively correlated. The two color component values are negatively correlated, and the adjusted third color component value is negatively correlated with the third color component value. If the first color component value is greater than the second color component value and the third color component value, but less than the correction threshold value, the adjusted first color component value and the gamma correction value of the first color component value are positively correlated, after adjustment The second color component value is negatively correlated with the gamma correction value of the second color component value, and the adjusted third color component value is negatively correlated with the gamma correction value of the third color component value.
1:影像系統 1: Video system
10:投影裝置 10: Projection device
12:色彩感測器 12: Color sensor
14:電腦 14: computer
140:處理器 140: Processor
16:投影表面 16: Projection surface
30:刺激點 30: Stimulus point
32:近端場 32: Proximal field
34:背景區域 34: Background area
36:環繞區域 36: Surrounding area
Sd:測量訊號 Sd: measurement signal
Simg:影像訊號 Simg: video signal
200,600:影像校正方法 200,600: image correction method
S202至S224,S602至S614:步驟 S202 to S224, S602 to S614: steps
50:原始影像之RGB顏色成分之亮度分布 50: The brightness distribution of the RGB color components of the original image
52:校正後影像的最大亮度成分之亮度分布 52: Brightness distribution of the maximum brightness component of the corrected image
54:校正後影像的非最大亮度成分之亮度分布 54: Brightness distribution of the non-maximum brightness components of the corrected image
第1圖係為本發明實施例中一種影像系統的方塊圖。 FIG. 1 is a block diagram of an imaging system in an embodiment of the present invention.
第2圖係為第1圖中之影像系統的一種影像校正方法之流程圖。 Fig. 2 is a flowchart of an image correction method of the image system in Fig. 1.
第3圖係為第1圖中之影像系統的一種量測區域之示意圖。 Fig. 3 is a schematic diagram of a measurement area of the image system in Fig. 1.
第4圖顯示第1圖中之投影裝置之一種調整介面之示意圖。 FIG. 4 shows a schematic diagram of an adjustment interface of the projection device in FIG. 1 .
第5圖係為本發明實施例中一種影像的底亮及伽馬校正之示意圖。 Fig. 5 is a schematic diagram of the background brightness and gamma correction of an image in an embodiment of the present invention.
第6圖係為第1圖中之影像系統的另一種影像校正方法之流程圖。 Fig. 6 is a flowchart of another image correction method of the image system in Fig. 1.
第1圖係為本發明實施例中一種影像系統1的方塊圖。影像系統1可不受環境光影響而維持影像的色外貌一致性,使環境光下色外貌表現與暗房中達到一致的效果。 FIG. 1 is a block diagram of an imaging system 1 in an embodiment of the present invention. The image system 1 can maintain the consistency of the color appearance of the image without being affected by the ambient light, so that the color appearance under the ambient light is consistent with that in the darkroom.
影像系統1包含投影裝置10、色彩感測器12、電腦14及投影表面16。電腦14可包含處理器140。投影裝置10及色彩感測器12可透過通用串列匯流排(universal serial bus,USB)、RS-232通訊埠介面或其他通訊介面耦接於處理器140。在一些實施例中,處理器140可位於投影裝置10中,且影像系統1可省略電腦14。色彩感測器12可為分光光度計(spectrophotometer)或分光光譜儀,例如X-rite i1Pro2、i1Studio、i1 Display Pro等螢幕校色器。投影表面16可為投影螢幕或牆面。色彩感測器12到投影表面16之間可具有預定距離,例如40公分。
The imaging system 1 includes a
影像系統1的測試環境可設置為環境光或暗室。在環境光,光源可為自然光及/或人造光。在暗室,光源會被遮蔽或關閉。處理器140可傳送影像訊號Simg至投影裝置10,投影裝置10可依據影像訊號Simg將影像投影至投影表面16,色彩感測器12可測量投影表面16及測試環境中不同波長的顏色成分之亮度以產生測量訊號Sd,及將測量訊號Sd傳送至處理器140,處理器140可依據測量訊號Sd校正投影裝置10的色域及/或進行對比度及飽和度的校正,藉以維持影像的色外貌一致性。
The test environment of the imaging system 1 can be set as ambient light or a dark room. In ambient light, the light source can be natural light and/or artificial light. In a dark room, the light source is shaded or turned off. The
第2圖係為影像系統1的一種影像校正方法200之流程圖,包含步驟S202至S224,用以維持影像的色外貌一致性。步驟S202至S208用以產生環境光下的色外貌表示值。步驟S210至S218用以校正投影裝置10的色域。步驟S220至S224用以進行影像的對比度及飽和度校正。任何合理的技術變更或是步驟調整都屬於本發明所揭露的範疇。以下說明步驟S202至S224:
步驟S202:於環境光下,色彩感測器12測量環境光背景亮度Yb;
步驟S204:於環境光下,控制投影裝置10使用第一色域將測試影像投影至投影表面16;步驟S206:於環境光下,色彩感測器12測量投影表面16上之測試影像的黑色之一組環境光測量值、白色之一組環境光測量值及至少一特定色之至少一組環境光測量值;步驟S208:處理器140依據黑色之該組環境光測量值、白色之該組環境光測量值、至少一特定色之至少一組環境光測量值、環境光的可適性區域亮度、環境光背景亮度及一組環境光環繞參數來產生黑色之一組色外貌表示值、白色之一組色外貌表示值及至少一特定色之至少一組色外貌表示值;步驟S210:於暗室下,控制投影裝置10將測試影像投影至投影表面16;步驟S212:於暗室下,色彩感測器12測量投影表面16上之測試影像的白色之一組暗室測量值及黑色之一組暗室測量值;步驟S214:處理器140判斷環繞比率Sr是否小於預定臨界值Srth?若是,繼續步驟S216;若否,則結束影像校正方法200。
FIG. 2 is a flow chart of an
步驟S216:處理器140依據至少一特定色之至少一組色外貌表示值、白色之該組暗室測量值、暗室的可適性區域亮度、暗室背景亮度及一組暗室環繞參數來產生至少一特定色之至少一組目標值;步驟S218:處理器140依據至少一特定色之至少一組目標值將投影裝置10設置至第二色域;步驟S220:處理器140將原始影像中之畫素的一組色值依據第二色域進行色域轉換以產生一組轉換色值,該組轉換色值包含第一顏色成分值、第二顏色成分值及第三顏色成分值;步驟S222:處理器140將黑色之該組色外貌表示值中之亮度加入第 一顏色成分值、第二顏色成分值及第三顏色成分值以分別產生調整後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值;步驟S224:於暗室下,投影裝置10投影調整後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值;結束影像校正方法200。 Step S216: The processor 140 generates at least one specific color according to at least one set of color appearance representation values of at least one specific color, the set of darkroom measurement values of white, the brightness of the adaptable area of the dark room, the background brightness of the dark room, and a set of ambient parameters of the dark room at least one set of target values; step S218: the processor 140 sets the projection device 10 to the second color gamut according to at least one set of target values of at least one specific color; step S220: the processor 140 sets one of the pixels in the original image The set of color values is subjected to color gamut conversion according to the second color gamut to generate a set of converted color values, the set of converted color values includes the first color component value, the second color component value and the third color component value; Step S222: Processor 140 Add the brightness in the appearance value of the group of black colors to the first A color component value, a second color component value and a third color component value to generate an adjusted first color component value, an adjusted second color component value and an adjusted third color component value; step S224: In a dark room, the projection device 10 projects the adjusted first color component value, the adjusted second color component value, and the adjusted third color component value; the image correction method 200 ends.
在步驟S202,在環境光下投影裝置10關閉,色彩感測器12測量投影表面16上之相對亮度(luminance)作為環境光背景亮度Yb。在一些實施例中,在環境光下投影裝置10亦可將參考黑色投影至投影表面16,色彩感測器12測量投影表面16上之參考黑色的亮度作為環境光背景亮度Yb。在另一些實施例中,色彩感測器12亦可測量背景區域之亮度以產生環境光背景亮度Yb。第3圖係為影像系統1的一種量測區域之示意圖,包含刺激點30、近端場32、背景區域34及環繞區域36。刺激點30係為投影裝置10之投影中心,近端場32係為色彩感測器12以刺激點30為中心向外擴張2%視角的範圍,背景區域34係為色彩感測器12從近端場32向外擴張達到10%視角的範圍,環繞區域36係為色彩感測器12從背景區域34向外擴張的範圍。由於環境光會主導影表面16上之參考黑色及背景區域34的亮度,上述三種方式獲得之環境光背景亮度Yb實質上相同。
In step S202 , the
在步驟S204,第一色域可為投影裝置10支援之最大色域,且大於或等於數位電影先導小組(Digital Cinema Initiatives,DCI)-P3色域。測試影像可包含黑色、白色及/或至少一特定色。至少一特定色包含六軸色全部或其中一種組合。六軸色包含紅、綠、藍、青(cyan)、洋紅(magenta)及黃色。每個顏色可由紅綠藍(red,green,blue,RGB)成分表示。例如,黑色(R,G,B)係為(0,0,0),白色(R,G,B)係為(255,255,255),紅色(R,G,B)係為(255,0,0),綠色(R,G,B)係為(0,255,0),藍色(R,G,B)係為(0,0,255),青色(R,G,B)係為(0,255,255),洋紅色(R,G,B)係為
(255,0,255),及黃色(R,G,B)係為(255,255,0)。由於在環境光會造成投影裝置10之色域的衰減,因此將投影裝置10之色域設置為大於或等於DCI-P3色域,以使投影裝置10在環境光的影響下盡可能維持在標準紅綠藍(standard red green blue,sRGB)的色域而不至於使投影裝置10之色域衰減到視覺效果無法接受的情況。
In step S204 , the first color gamut may be the maximum color gamut supported by the
在步驟S206,黑色之一組環境光測量值、白色之一組環境光測量值及至少一特定色之至少一組環境光測量值之每組環境光測量值可為三色刺激值(tri-stimulus),以國際照明委員會色外貌模型(international commission on illumination,CIE)XYZ表示。白色之該組環境光測量值可視為參考白色的XYZ值,參考白色的Y值可視為參考白色的絕對亮度(absolute luminance)Lw。例如,表1顯示環境光下色彩感測器12測量得之黑、白、紅、綠、藍、青、洋紅及黃色的測量值XYZ:
在步驟S208,處理器140依據色外貌模型(color appearance model,CAM)將每組環境光測量值轉換為一組色外貌表示值,該組色外貌表示值可包含CIE色外貌模型定義之明度(lightness,以J表示)、紅綠相關維度(a)及黃藍相關維度(b)。色外貌模型可為CIECAM02模型、CIECAM16模型或其他CIECAM模型,且CIECAM16的轉換模型可由公式(1)表示:Jab=XYZCAM16UCS(XYZ,XYZw,La,Yb,surround) 公式(1)
In step S208, the
其中 Jab係為一組色外貌表示值;XYZ係為測量所得之給定色的環境光測量值;XYZw係為參考白色之環境光測量值;La係為可適性區域亮度;Yb係為背景亮度;及surround係為環繞參數,包含適應程度因子F、環繞影響參數c及色彩感應因子Nc。 Among them, Jab is a group of color appearance representation values; XYZ is the ambient light measurement value of a given color measured; XYZw is the ambient light measurement value of reference white; La is the brightness of the adaptable area; Yb is the background brightness ; and surround is the surround parameter, including the adaptability factor F, the surround influence parameter c and the color sensing factor Nc.
可適性區域亮度La可由投影裝置10投影參考白色至投影表面16,及色彩感測器12直接測量投影表面16的刺激點30之參考白色的絕對亮度而獲得。在一些實施例中,可適性區域亮度La亦可使用參考白色的測量值依據公式(2)計算獲得。公式(2)如下:
其中 La係為可適性區域亮度;Lw係為參考白色的絕對亮度,單位為cd/m2;Ew係為參考白色的照度,單位為Lux,Ew=πLw;Yb係為背景亮度;及Yw係為可適性區域的參考白色的相對亮度。 Among them, the La system is the brightness of the adaptability area; the Lw system is the absolute brightness of the reference white, the unit is cd/m 2 ; the Ew system is the reference white illuminance, the unit is Lux, Ew=πLw; the Yb system is the background brightness; and the Yw system is the relative brightness of the reference white in the adaptability region.
在環境光下,色彩感測器12測量投影表面16上之亮度會得到可適性
區域的參考白色的相對亮度Yw。處理器140將參考白色的絕對亮度Lw、環境光背景亮度Yb及可適性區域的參考白色的相對亮度Yw代入公式(2)以計算環境光的可適性區域亮度La。
In ambient light, the
處理器140計算環繞比率Sr。環繞比率Sr可由公式(3)表示:Sr=Lsw/Ldw 公式(3)
The
其中 Sr係為環繞比率;Lsw係為環繞區域的投影表面的絕對亮度;及Ldw係為顯示區域的白色的絕對亮度。 where Sr is the surround ratio; Lsw is the absolute luminance of the projection surface of the surrounding area; and Ldw is the absolute luminance of white in the display area.
公式(3)顯示環繞比率Sr為環繞區域的投影表面的絕對亮度Lsw對顯示區域的白色的絕對亮度Ldw的比率。在一些實施例中,環境光背景亮度Yb可視為環繞區域的白色的絕對亮度Lsw,參考白色的絕對亮度Lw可視為顯示區域的白色的絕對亮度Ldw,接著處理器140依據公式(3)計算環境光背景亮度Yb及參考白點的相對亮度Lw之環繞比率Sr。在一些實施例中,色彩感測器12亦可測量投影表面16上之白色之亮度及環繞區域36之亮度,及處理器140依據公式(3)計算投影表面16上之白色之亮度及環繞區域36之亮度之環繞比率Sr。
Formula (3) shows that the surround ratio Sr is the ratio of the absolute luminance Lsw of the projection surface of the surrounding area to the absolute luminance Ldw of white in the display area. In some embodiments, the ambient light background brightness Yb can be regarded as the absolute brightness Lsw of white in the surrounding area, the absolute brightness Lw of reference white can be regarded as the absolute brightness Ldw of white in the display area, and then the
處理器140依據環繞比率Sr從下表2獲得適應程度因子F、環繞影響參數c及色彩感應因子Nc等環繞參數surround。
The
表2顯示CIECAM16定義之3種環境狀態,分別為平均環境、亮室環境及暗室,每種環境狀態分別對應各自之適應程度因子F、環繞影響參數c及色彩感應因子Nc。例如,當環繞區域的投影表面的絕對亮度Lsw為10尼特,且顯示區域的白色的絕對亮度Ldw為50尼特時,環繞比率Sr為0.2(=10/50),環繞參數surround包含適應程度因子F為0.9,環繞影響參數c為0.59及色彩感應因子Nc為0.95。給定色之該組環境光測量值XYZ、參考白色之該組環境光測量值XYZw及環境光背景亮度Yb已於步驟S202及S206獲得。給定色可為黑色、白色或任一特定色。處理器140將給定色之該組環境光測量值XYZ、參考白色之該組環境光測量值XYZw、環境光的可適性區域亮度La、環境光背景亮度Yb及環繞參數surround代入公式(1)以計算給定色之該組色外貌表示值Jab。例如,環境光背景亮度Yb可為5.63,環境光的可適性區域亮度La可為13.41,黑、白、紅、綠、藍、青、洋紅及黃色的Jab值可如表3所示:
在步驟S210及S212,環境光源被關閉,且影像系統1處於暗室,投影裝置10將測試影像投影至投影表面16,測試影像包含黑色及/或白色。色彩感測器12測量投影表面16上之測試影像的白色之一組暗室測量值以獲得暗室的可適性區域亮度La,及測量投影表面16上之測試影像的黑色之一組暗室測量值以獲得暗室背景亮度Yb。白色之該組暗室測量值及黑色之該組暗室測量值可以CIE XYZ表示。白色之該組暗室測量值可視為參考白色的XYZ值,參考白色的Y值可視為參考白色的暗室絕對亮度Lw。
In steps S210 and S212 , the ambient light source is turned off, and the image system 1 is in a dark room, the
在步驟S214,處理器140判定環繞比率Sr是否小於預定臨界值Srth。預定臨界值Srth可為0.2。若環繞比率Sr小於預定臨界值Srth,則環境狀態為環境光或暗室,當環境狀態變為其他環境光或暗室時,投影裝置10仍具有足夠的色域調整範圍以維持色外貌一致性,因此影像校正方法200繼續步驟S216。若環繞比率Sr大於預定臨界值Srth,則環境狀態為平均環境,當環境狀態變為暗室或環境光時,投影裝置10的色域調整範圍不足以維持色外貌一致性,因此影像校正方法200結束。
In step S214, the
在步驟S216,處理器140依據色外貌模型將步驟S210產生之每組色外貌表示值逆轉換為暗室之一組目標值,每組目標值可以CIE XYZ表示。CIECAM16的逆轉換模型可由公式(4)表示:XYZ=CAM16UCSXYZ(Jab,XYZw,La,Yb,surround) 公式(4)
In step S216, the
其中 XYZ係為暗室之一組目標值;Jab係為一組色外貌表示值;XYZw係為參考白色之暗室測量值; La係為暗室的可適性區域亮度;Yb係為暗室背景亮度;及surround係為暗室環繞參數,包含適應程度因子F、環繞影響參數c及色彩感應因子Nc。 Among them, XYZ is a group of target values in the darkroom; Jab is a group of color appearance representation values; XYZw is the darkroom measurement value of reference white; La is the adaptive area brightness of the darkroom; Yb is the background brightness of the darkroom; and surround is the surrounding parameters of the darkroom, including the adaptability factor F, the surround influence parameter c and the color sensing factor Nc.
環繞區域的投影表面的絕對亮度Lsw可為色彩感測器12從背景區域34量測的亮度,且會實質上等於0。白色之暗室測量值Y可視為暗室參考白色的絕對亮度Lw及顯示區域的白色的絕對亮度Ldw,處理器140將環繞區域的投影表面的絕對亮度Lsw(0)及顯示區域的白色的絕對亮度Ldw代入公式(3)以計算暗室環繞比率Sr(0),進而從表2獲得暗室環繞參數surround。暗室的可適性區域亮度La可在暗室下由色彩感測器12直接測量投影表面16中央區域之參考白色的絕對亮度而獲得。該組色外貌表示值Jab從步驟S208獲得,且可為黑色、白色或至少一特定色之一組色外貌表示值Jab。處理器140將該組色外貌表示值Jab、參考白色之暗室測量值XYZw、暗室的可適性區域亮度La、暗室背景亮度Yb及暗室環繞參數surround代入公式(4)以計算該組目標值XYZ。例如,例如,暗室背景亮度Yb可為0.13,暗室的可適性區域亮度La可為0.03,黑、白、紅、綠、藍、青、洋紅及黃色的目標值XYZ可如表4所示:
在步驟S218,處理器140依據至少一特定色之至少一組目標值調整至少一特定色之至少一色溫增益、至少一色調及至少一飽和度以將投影裝置10設置至第二色域。在一些實施例中,第二色域的範圍係小於第一色域。在一些實施例中,使用者可依據至少一特定色之至少一組目標值輸入一組調整值,處理器140可接收該組調整值及依據該組調整值調整至少一特定色之至少一色溫增益(gain)、至少一色調(hue)及至少一飽和度(saturation),色彩感測器12可即時量測至少一特定色之至少一組更新測量值,使用者可依據至少一特定色之至少一組目標值及至少一組更新測量值另輸入一組調整值,直到至少一特定色之至少一組目標值及至少一組更新測量值匹配為止。第4圖顯示一種投影裝置10之調整介面,用以輸入至少一特定色之一組調整值。在另一些實施例中,色彩感測器12可即時量測至少一特定色之至少一組更新測量值,處理器140亦可依據至少一特定色之至少一組目標值及至少一組更新測量值自動調整至少一特定色之至少一色溫增益、至少一色調及至少一飽和度,直到至少一特定色之至少一組目標值及至少一組更新測量值匹配為止。在一些實施例中,至少一特定色可包含六軸色,處理器140依據六軸色之6組目標值調整六軸色之6組色溫增益、色調及飽和度以將投影裝置10設置至第二色域。在一些實施例中,處理器140可另調整至少一特定色之至少一亮度(brightness)以將投影裝置10設置至第二色域。
In step S218 , the
在步驟S220,該組轉換色值可為一組RGB轉換色值,第一顏色成分值可為紅色成分值,第二顏色成分值可為綠色成分值及第三顏色成分值可為藍 色成分值。 In step S220, the set of converted color values can be a set of RGB converted color values, the first color component value can be a red component value, the second color component value can be a green component value and the third color component value can be blue Color component value.
在步驟S222,處理器140對該組RGB轉換色值進行底亮(最低亮度)校正及伽馬校正(Gamma correction)以校正對比度及飽和度。由於在環境光下,影像的亮度會抬高且對比度會降低,因此處理器140另對該組RGB轉換色值進行底亮及伽馬校正,以在暗室模擬環境光下的影像亮度及對比度,同時增加飽和度。
第5圖係為處理器140進行底亮及伽馬校正之示意圖,其中橫軸表示調整前之256階亮度(luminance)Lin,縱軸表示調整後之256階亮度Lout。曲線50顯示原始影像之RGB顏色成分之亮度分布;曲線52顯示校正後影像的最大亮度成分之亮度分布;曲線54顯示校正後影像的非最大亮度成分之亮度分布。最大亮度成分可為RGB顏色成分中具有最大亮度之顏色成分,且非最大亮度成分可為RGB顏色成分中不具有最大亮度之顏色成分。最大亮度成分可由公式(5)獲得:Cmax=Max(Rin,Gin,Bin) 公式(5)
In step S222 , the
其中 Cmax係為最大亮度成分值;及Rin,Gin,Bin係分別為影像像素之調整前的紅、綠、藍色成分值。 Among them, Cmax is the maximum brightness component value; and Rin, Gin, Bin are the red, green and blue component values of the image pixel before adjustment respectively.
若第一顏色成分值大於第二顏色成分值、第三顏色成分值,則第一顏色成分值對應最大亮度之顏色成分,第二顏色成分值及第三顏色成分值對應非最大亮度之顏色成分。原始影像之RGB顏色成分之輸入輸出亮度分布50係為線性,且最小輸出亮度為0階。當進行底亮校正時,處理器140將黑色之該組色外貌表示值中之黑色亮度成分值Jb加入RGB顏色成分以抬高影像的亮度。當進行伽馬校正時,若最大亮度之顏色成分值Cmax小於校正臨界值Iref,則調整後之第一顏色成分值和調整前第一顏色成分值之伽馬校正值成正相關,調整後之第二顏色成分值和調整前第二顏色成分值之伽馬校正值成負相關,及調整後之第三顏色成分值和調整前第三顏色成分值之伽馬校正值成負相關,由公式(6)、(7)、
(8)表示:Rout=((255-Cmax)/255*Jb)+(Rin/255)γ*(255-(255-Cmax)/255*Jb) 公式(6)
If the first color component value is greater than the second color component value and the third color component value, the first color component value corresponds to the color component with the maximum brightness, and the second color component value and the third color component value correspond to the color component without the maximum brightness . The input and
Gout=((255-Cmax)/255*Jb)+(Gin/255)γ*(255-(255-Cmax)/255*Jb) 公式(7) Gout=((255-Cmax)/255*Jb)+(Gin/255) γ *(255-(255-Cmax)/255*Jb) formula (7)
Bout=((255-Cmax)/255*Jb)+(Bin/255)γ*(255-(255-Cmax)/255*Jb) 公式(8) Bout=((255-Cmax)/255*Jb)+(Bin/255) γ *(255-(255-Cmax)/255*Jb) formula (8)
其中 Rout,Gout,Bout係分別為影像像素之調整後的紅、綠、藍色成分值;Rin,Gin,Bin係分別為影像像素之調整前的紅、綠、藍色成分值;Jb係為黑色亮度成分值;Cmax係為最大亮度成分值;及γ係為伽馬值。 Among them, Rout, Gout, and Bout are respectively adjusted red, green, and blue component values of image pixels; Rin, Gin, and Bin are respectively red, green, and blue component values of image pixels before adjustment; Jb is Black luminance component value; Cmax system is the maximum luminance component value; and γ system is the gamma value.
在第5圖中,校正臨界值Iref約為105,當小於校正臨界值Iref時,曲線52顯示最大亮度成分之調整後的亮度和調整前的亮度的伽馬校正值成正相關,且最大亮度成分之調整後的最小輸出亮度約為50階;曲線54顯示非最大亮度成分之調整後的亮度和調整前的亮度的伽馬校正值成負相關,且非最大亮度成分之調整後的最大輸出亮度約為50階。
In Figure 5, the correction critical value Iref is about 105. When it is less than the correction critical value Iref, the
若最大亮度之顏色成分Cmax大於校正臨界值Iref,則調整後之第一顏色成分值和調整前第一顏色成分值成正相關,調整後之第二顏色成分值和調整前第二顏色成分值成負相關,及調整後之第三顏色成分值和調整前第三顏色成分值成負相關,由公式(9)、(10)、(11)表示。 If the color component Cmax of the maximum brightness is greater than the correction critical value Iref, the value of the first color component after adjustment is positively correlated with the value of the first color component before adjustment, and the value of the second color component after adjustment is proportional to the value of the second color component before adjustment. Negative correlation, and the value of the third color component after adjustment is negatively correlated with the value of the third color component before adjustment, expressed by formulas (9), (10), and (11).
Rout=((255-Cmax)/255*Jb)+(Rin/255)1.0*(255-(255-Cmax)/255*Jb) 公式(9) Rout=((255-Cmax)/255*Jb)+(Rin/255) 1.0 *(255-(255-Cmax)/255*Jb) formula (9)
Gout=((255-Cmax)/255*Jb)+(Gin/255)1.0*(255-(255-Cmax)/255*Jb) 公式(10) Gout=((255-Cmax)/255*Jb)+(Gin/255) 1.0 *(255-(255-Cmax)/255*Jb) formula (10)
Bout=((255-Cmax)/255*Jb)+(Bin/255)1.0*(255-(255-Cmax)/255*Jb) 公式(11) Bout=((255-Cmax)/255*Jb)+(Bin/255) 1.0 *(255-(255-Cmax)/255*Jb) formula (11)
其中 Rout,Gout,Bout係分別為影像像素之調整後的紅、綠、藍色成分值;Rin,Gin,Bin係分別為影像像素之調整前的紅、綠、藍色成分值;Jb係為黑色亮度成分值;及Cmax係為最大亮度成分。 Among them, Rout, Gout, and Bout are respectively adjusted red, green, and blue component values of image pixels; Rin, Gin, and Bin are respectively red, green, and blue component values of image pixels before adjustment; Jb is black luminance component value; and Cmax is the maximum luminance component.
在第5圖中,當大於校正臨界值Iref時,曲線52顯示最大亮度成分之調整後的亮度和調整前的亮度成正相關;曲線54顯示非最大亮度成分之調整後的亮度和調整前的亮度成負相關。
In Figure 5, when it is greater than the correction critical value Iref, the
在步驟S224,投影裝置10投影每個畫素之調整後的紅、綠、藍色成分值,藉以維持暗室及環境光的色外貌一致性。
In step S224, the
雖然實施例提供維持暗室及環境光的色外貌一致性的方法,熟習此技藝者亦可依據影像校正方法200相同的原則來維持不同的環境光之色外貌一致性。
Although the embodiment provides a method for maintaining the color appearance consistency of the dark room and ambient light, those skilled in the art can also maintain the color appearance consistency of different ambient lights according to the same principle of the
影像系統1及影像校正方法200透過色外貌模型的轉換而調整投影裝置10的色域,同時透過影像處理調整影像的對比度及飽和度,藉以實現暗室及環境光的色外貌一致性。
The image system 1 and the
第6圖係為影像系統1的另一種影像校正方法600之流程圖,包含步驟S602至S614,用以維持影像的色外貌一致性。步驟S602至S608用以產生環境光下的色外貌表示值。步驟S610至S614用以進行影像的對比度及飽和度校正。任何合理的技術變更或是步驟調整都屬於本發明所揭露的範疇。以下說明步驟S602至S614:步驟S602:於環境光下,色彩感測器12測量環境光背景亮度Yb;步驟S604:於環境光下,控制投影裝置10使用預定色域將測試影像投影至投影表面16;步驟S606:於環境光下,色彩感測器12測量投影表面16上之測試影像的黑色之一組環境光測量值及白色之一組環境光測量值;步驟S608:處理器140依據黑色之該組環境光測量值、白色之該組環境光測量值、環境光的可適性區域亮度、環境光背景亮度及一組環境光環繞參數來產生黑色之一組色外貌表示值;步驟S610:處理器140將原始影像中之畫素的一組色值依據第二色域進行色域轉換以產生一組轉換色值,該組轉換色值包含第一顏色成分值、第二顏色成分值及第三顏色成分值;步驟S612:處理器140將黑色之該組色外貌表示值中之亮度加入第一顏色成分值、第二顏色成分值及第三顏色成分值以分別產生調整後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值;步驟S614:於暗室下,投影裝置10投影調整後之第一顏色成分值、調整後之第二顏色成分值及調整後之第三顏色成分值。
FIG. 6 is a flow chart of another
除了測試影像可包含黑色及/或白色,及只需產生黑色之一組色外貌表示值之外,步驟S602至S608和步驟S202至S208相似。步驟S610至S614和步驟S220至S224相似,其細節可於前述段落中找到,在此不再贅述。 Steps S602 to S608 are similar to steps S202 to S208 except that the test image may contain black and/or white, and only a set of color appearance representation values of black is required to be generated. Steps S610 to S614 are similar to steps S220 to S224, and the details thereof can be found in the preceding paragraphs, and will not be repeated here.
影像系統1及影像校正方法600透過影像處理調整影像的對比度及飽和度,藉以實現暗室及環境光的色外貌一致性。以上所述僅為本發明之較佳實施例,凡依本發明申請專利範圍所做之均等變化與修飾,皆應屬本發明之涵蓋範圍。
The image system 1 and the
200:影像校正方法 200: Image Correction Method
S202至S224:步驟 S202 to S224: Steps
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