G. E. Legge and J. M. Foley, "Contrast masking in human vision," J. Opt. Soc. Amer. A, vol. 70, no. 12, pp. 1458--1471, 1980.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....The addition of contrast masking allows for even more dynamic control of the JND threshold levels. Contrast masking refers to the detectability of one signal in the presence of another signal; the effect is strongest when both signals are of the same spatial frequency, orientation and location [13,14]. The most effective visual models should take into account frequency sensitivity, local luminance sensitivity and contrast masking. The choice of the analysis filter bank used in a coder can affect the performance of the compression system and how effectively visual masking can be utilized. In ....

G. E. Legge and J.M. Foley, "Contrast masking in human vision," Journal of the Optical Society of America, vol. 70, no. 12, December, 1980, pp. 1458-1471.

....The addition of contrast masking allows for even more dynamic control of the JND threshold levels. Contrast masking refers to the detectability of one signal in the presence of another signal; the effect is strongest when both signals are of the same spatial frequency, orientation and location [7]. The most effective visual models should take into account frequency sensitivity, local luminance sensitivity and contrast masking. JPEG is the current international standard for color still image compression [8] The most basic version of this coder, the Baseline Sequential Codec, consists of ....

G. E. Legge and J.M. Foley, "Contrast masking in human vision," Journal of the Optical Society of America, vol. 70, no. 12, December, 1980, pp. 1458-1471.

....and small noise adding. Zhu et al. 4] propose two techniques based on spatial and frequency masking. Their watermark is guaranteed to be perceptually invisible, yet it can detect errors up to one half of the maximal allowable change in each pixel or frequency bin depending on whether frequency [5] or spatial [6] masking is used. The image is divided into blocks and in each block a secret random signature (a pseudo random sequence uniformly distributed in [0,1] is multiplied by the masking values of that block. The resulting signal depends on the image block and is added to the original ....

....60 55 14 13 16 24 40 57 69 56 14 17 22 29 51 87 80 62 18 22 37 56 68 109 103 77 24 35 55 64 81 104 113 92 49 64 78 87 103 121 120 101 72 92 95 98 112 100 103 99] The quantized values are further binary encoded. The bit lengths of their codes (including the signs) are shown in matrix L L=[7 7 7 5 4 3 2 1 7 6 5 5 4 2 1 0 6 5 5 4 3 1 0 0 5 5 4 3 1 0 0 0 4 4 3 1 0 0 0 0 3 2 1 0 0 0 0 0 2 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0]. Coding based on L will guarantee that the first 11 coefficients from each block will be coded using exactly 64 bits. In the rare event when the i th DCT coefficient has absolute value is larger than 2 Li , only this maximum available value will be encoded. Step 3 (Encrypting and embedding) ....

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision", J. Opt. Soc. Am., 70(12), pp. 1458-1471, 1980.

....a signal raises the visual threshold for other signals around it. Both frequency and spatial masking are employed by our watermarking scheme. Our frequency masking model is based on the observation that a masking grating raises the visual threshold for signal gratings around the masking frequency [10]. The model we use [11] expresses the contrast threshold at frequency f as a function of f , the masking frequency fm and the masking contrast c m : c(f,f m) c 0 (f)Max 1, k(f f m )c m ] # , where c 0 (f) is the detection threshold at frequency f . To find the contrast threshold ....

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision," J. Opt. Soc. Am., vol. 70, no. 12, pp. 1458--1471, 1980.

....separation between states corresponding to di erent bit sequences, and thus achieve robust data hiding. One solution to this problem (of trying to introduce as much distortion as possible without a ecting the visual delity) is to use good models of visual thresholds (for example, see Ref. [1]) to embed the hidden bits. Many data hiding methods that utilize these models have been proposed. However, a main draw back of these methods is that well de ned visual threshold models (say in the DCT or wavelet domain) also suggest the compression techniques means to improve their performance. ....

G.E. Legge, J.M. Foley, \Contrast Masking in Human Vision", Journal of Optical Society of America, 70, No 12, pp 1458-1471, 1980.

....found in [18] We are currently developing a watermarking algorithm that takes temporal masking (e.g. 19] into account. A. Frequency Masking Our frequency masking model is based on the knowledge that a masking grating raises the visual threshold for signal gratings around the masking frequency [20]. The model we use [18] based on the discrete cosine transform (DCT) expresses the contrast threshold at frequency as a function of the masking frequency and the masking contrast (1) where the detection threshold at frequency and are determined by psychovisual tests [20] The mask weighting ....

.... the masking frequency [20] The model we use [18] based on the discrete cosine transform (DCT) expresses the contrast threshold at frequency as a function of the masking frequency and the masking contrast (1) where the detection threshold at frequency and are determined by psychovisual tests [20]. The mask weighting function is shown in Fig. 1. To find the contrast threshold at a frequency in an image, we first use the DCT to transform the image into the frequency domain and find the contrast at each frequency. Then, we use a summation rule of the form (2) to sum up the masking effects ....

G. E. Legge and J. M. Foley, "Contrast masking in human vision," J. Opt. Soc. Amer., vol. 70, no. 12, pp. 1458--1471, 1980.

....order to model in band masking effects in the frequency bands and orientations, a contrast transducer function is used. The contrast transducer function saturates at high contrasts, and accelerates at low contrasts, which is in accordance with contrast discrimination experiments by Legge and Foley [19]. The contrast transducer is given by: 6) C out x y t k l , aC x y t k l , b C x y t k l , 2 g = where C(x,y,t,k,l) is the input contrast at position (x,y) at time instant t in the frequency band with index ....

Legge, G.E., and J.M. Foley, "Contrast masking in human vision", Journal of the Optical Society of America, vol. 70, pp 1458-1471, 1980.

....around it. The masking values are obtained by the threshold visual masking models that were used in high quality, low bit rate image coding [3] In the frequency domain, a grating signal raises the perceptual thresholds of other gratings whose frequencies are close to the masking frequency [4]. If the masking frequency is f m , and the masking contrast is c m , the contrast threshold at f due to the masker f m is modeled as c(f; f m ) c 0 (f) Delta Maxf1; k(f=f m )c m ] ff g; 1) where c 0 (f) is the detection threshold at frequency f . Since we use discrete cosine transform ....

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision," J. Opt. Soc. Am., Vol 70, No. 12, PP. 1458-1471, 1980.

....are three free parameters: a scale factor, a, an exponent, p, and the contrast gain, s. The hyperbolic ratio describes single cell contrast response functions (Albrecht and Hamilton, 1982; Sclar et al. 1990) The formula also has been used to fit psychophysical data on contrast discrimination (Legge and Foley, 1980; Foley and Boynton, 1993) We modeled the temporal impulse response with a gamma function: h t 5 t t n21 e 2 t t t n 2 1 , 3) Figure 8. fMRI responses from shorter pulses can predict the responses to longer pulses. The four principal component curves (corresponding to pulse ....

Legge GE, Foley JM (1980) Contrast masking in human vision. J Opt Soc Am A 70:1458 --1470.

....is called the absolute threshold. As the baseline contrast increases above zero, the increment threshold drops below the absolute threshold. This effect is called negative masking, facilitation, or the pedestal effect (Nachmias Sansbury, 1974; Stromeyer Klein, 1974; Tolhurst Barfield, 1977; Legge Foley, 1980). As the baseline contrast increases beyond the range of facilitation, the increment threshold increases well above the absolute threshold. This increase in increment thresholds for high baseline contrasts is called masking. A popular class of models predict the form of the TvC function by ....

....Science Ltd. All rights reserved. PII: S0042 6989(98)00113 8 G.M. Boynton et al. Vision Research 39 (1999) 257 269 258 nonlinearity. According to these models an increment in contrast can be detected only when the increment in the neuronal response increases by some criterion amount (Legge Foley, 1980; Foley Yang, 1991; Foley, 1994; Foley Boynton, 1994; Teo Heeger, 1994, 1995) The shape of the TvC function is therefore a simple consequence of the shape of the neuronal contrast response function; increment thresholds are inversely related to the slope of the neuronal contrast ....

[Article contains additional citation context not shown here]

Legge, G. E., & Foley, J. M. (1980). Contrast masking in human vision. Journal of the Optical Society of America A, 70, 1458 -- 1470.

....and orientations. Interactions between image components within these bands result in masking effects like the ones illustrated in Figures 28 and 29 where the visual response to one component depends upon the presence of other components. The parameters of these masking effects were investigated by Legge and Foley (1980). Legge and Foley performed a series of experiments to determine how the presence of one grating affects 23 Figure 29: Demonstration of critical band masking: a) consists of a continuous tone photograph that has been low pass filtered to 10 cycles picture height and then coarsely sampled and ....

Legge, G.E. and Foley, J.M. (1980). Contrast masking in human vision. J. Opt. Soc. Am., 70, 1458-1470.

....plotted on its own arbitrary scale. The dotted line through each curve indicates the unmasked threshold for the 2.0 cycle degree test grating. Note that the curves show a pattern of facilitation or increased sensitivity at low mask contrasts and threshold elevation at higher mask contrasts. From [Legge80]. nel and two chromatic channels, one tuned to a red green dimension and the other to a yellow blue dimension. If we want to predict masking e#ects in complex color images we need to correctly model masking in both the chromatic and achromatic visual channels. Figure 10: a) Chromatic contrast ....

Legge, G.E. and Foley, J.M. (1980). Contrast masking in human vision. J. Opt. Soc. Am., 70, 1458-1470.

....and small noise adding. Zhu et al. 4] propose two techniques based on spatial and frequency masking. Their watermark is guaranteed to be perceptually invisible, yet it can detect errors up to one half of the maximal allowable change in each pixel or frequency bin depending on whether frequency [5] or spatial [6] masking is used. The image is divided into blocks and in each block a secret random signature (a pseudo random sequence uniformly distributed in [0,1] is multiplied by the masking values of that block. The resulting signal depends on the image block and is added to the original ....

....19 26 58 60 55 14 13 16 24 40 57 69 56 14 17 22 29 51 87 80 62 18 22 37 56 68 109 103 77 24 35 55 64 81 104 113 92 49 64 78 87 103 121 120 101 72 92 95 98 112 100 103 99] The quantized values are further binary encoded. The bit lengths of their codes (including the signs) are shown in matrix L L=[7 7 7 5 4 3 2 1 7 6 5 5 4 2 1 0 6 5 5 4 3 1 0 0 5 5 4 3 1 0 0 0 4 4 3 1 0 0 0 0 3 2 1 0 0 0 0 0 2 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0]. Coding based on L will guarantee that the first 11 coefficients from each block will be coded using exactly 64 bits. In the rare event when the i th DCT coefficient has absolute value is larger than 1 2 i L , only this maximum available value will be encoded. Step 3 (Encrypting and ....

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision", J. Opt. Soc. Am., 70(12), pp. 1458--1471, 1980.

....uses models of the human visual system to design provably invisible watermarks. The authors utilize spatial and frequency masking phenomena to guarantee watermark s invisibility. An image is first divided into blocks of 8 8 pixels. Each block is DCT transformed and a frequency masking model [Leg1] is used to calculate maximal allowable changes in each DCT frequency bin. The frequency masking phenomenon relates to the fact that one signal may mask the presence of another, weaker signal of similar frequency thus making it invisible. For example, sinusoidal grating of frequency f and ....

....M N video frame is divided into blocks of 8 8 pixels. Each block B is transformed using a DCT together with author s signature S. The transformed signature is normalized so that its maximal values are within the unit interval. The DCT transform of B is analyzed using a frequency masking model [Leg1] Maximal allowable changes of all 64 DCT coefficients are calculated. Let T denote the minimum of those allowable changes. The transformed block is projected onto a random direction that is obtained as a DCT transform of the normalized signature S. The projection value p is modified to p by ....

[Article contains additional citation context not shown here]

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision", J. Opt. Soc. Am., 70(12), pp. 1458--1471, 1980.

....texture varies directly with the contrast of the pattern. For high contrast patterns, however, factors other than contrast may determine the perceived pattern strength [8] Since the task involved the detection of a pattern on a uniform gray field, we did not need to model visual masking [6]. Masking occurs when a high contrast pattern is on or near the stimulus. The masking pattern may reduce sensitivity to the pattern. In developing quality metrics for printers, it is usually more useful to know the detectability of distortion on a uniform field, since this is the worst case of ....

G. E. Legge and J. M. Foley. Contrast Masking in Human Vision. Journal of the Optical Society of America, 70(12):1458--1471, December 1980.

....a signal raises the visual threshold for other signals around it. Both frequency and spatial masking are employed by our watermarking scheme. Our frequency masking model is based on the observation that a masking grating raises the visual threshold for signal gratings around the masking frequency [10]. The model we use [11] expresses the contrast threshold at frequency f as a function of f , the masking frequency fm and the masking contrast c m : c(f; fm ) c 0 (f) Delta Maxf1; k(f=f m )c m ] ff g; where c 0 (f) is the detection threshold at frequency f . To find the contrast threshold ....

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision," J. Opt. Soc. Am., vol. 70, no. 12, pp. 1458--1471, 1980.

.... Delta 2 e Gamma Gamma Gamma 0 Delta Delta 2 ; 2) where Deltak = 0:5, Delta = 8. The filters, shown in Figure 3, are chosen to model the visual channels [8] Each channel of the distorted image is compared to the same channel from the original image and a masking model applied [5]. The masking model used here allows only within channel masking and uses masking weights computed as the inverse the normalised detection threshold: C T = 1 CM C T0 i CM CT 0 j 2:5 CM C T0 (3) where C T0 = k f C) 0:62 is the detection threshold of the error in the absence of the ....

G.Legge and J. Foley. Contrast masking in human vision. Journal of the Optical Society of America, 70(12):1458--1471, 1980.

....are. This effect is known as the luminance masking. An experimental study of the luminance masking can be found in [AhP92] Another effect on the sensibility of the human visual system is the contrast masking, which refers to the reduction in the visibility of one image component by another [LeF80, Leg81]. After the thresholds obtained under normal conditions are adjusted by the luminance masking and the contrast masking, they become justnoticeable differences (JNDs) for the particular background and image pattern. A human being will notice a viewing distortion if the error intensity for a ....

G. E. Legge and J. M. Foley, "Contrast masking in human vision," J. Optical Society of America, Vol. 70, Dec. 1980, pp. 14581471.

....Zhu et al. 5] propose two techniques based on spatial and frequency masking. Their watermark is guaranteed to be perceptually invisible, yet it can detect errors up to one half of the maximal allowable change in each pixel or frequency bin depending on whether spatial [6] or frequency [7] masking is used. The image is divided into blocks and in each block a secret random signature (a pseudo random sequence uniformly distributed in [0,1] is multiplied by the masking values of that block. The resulting signal depends on the image block and is added to the original block quantized ....

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision", J. Opt. Soc. Am., 70(12), pp. 1458--1471, 1980.

....our metrics to incorporate more perceptual factors that influence color difference perception. Other factors that affect perceptual fidelity measurements include, but are not limited to, the adaptation of the eye to ambient illumination [13 17] contrast masking effect of spatial patterns [18 20], and higher level cognitive processes such as memory and attention [21] Other color image metrics exist that take into account one or more of these effects, such as DCTune [22] For this paper, however, we will limit our scope to the three metrics described above, because they are all simple ....

....coarse quantization of high frequency components, and (2) the block processing structure of the algorithm. In the case of quantization, the errors are typically correlated with lines or edges in the images, and therefore hidden by the effect of orientation selective masking and contrast masking [18,28 30]. The RMS, CIELAB, or S CIELAB metrics do not include effects of contrast masking or orientation selective masking. These metrics should not be expected to make accurate predictions about visibility of JPEG artifacts. 4 Conclusions Subjects identified visible reproduction errors in a collection of ....

G. G. E. Legge and J. M. Foley, "Contrast masking in human vision," Journal of the Optical Society of America 70, pp. 1458--1471, 1980.

....of 1, so that only suprathreshold contrasts produce any masking. The exponent w u,v,f is allowed to vary with frequency and perceptual color channel, but we have typically used a constant value of 0.7. This masking model is derived from classical results on masking of sinusoidal luminance gratings[10, 11]. We have recently provided psychophysical evidence that it is also a reasonable model for masking of DCT luminance basis functions[7] The limited information on masking within the chromatic channels [12] suggests essentially similar behavior. This model of masking explicitly assumes that ....

Legge, G. E. and J. M. Foley. Contrast masking in human vision. Journal of the Optical Society of America. 70(12): 14581471, 1980.

....for other signals around it. Masking characteristics are used in high quality low bit rate coding algorithms to further reduce bit rates [6] Our frequency masking model is based on the knowledge that a masking grating raises the visual threshold for signal gratings around the masking frequency [7]. The model we use [8] expresses the contrast threshold at frequency f as a function of f , the masking frequency f m and the masking contrast c m . To find the contrast threshold c(f) at a frequency f in an image, we first use the DCT to transform the image into the frequency domain and find the ....

G. E. Legge and J. M. Foley, "Contrast Masking in Human Vision," J. Opt. Soc. Am., vol. 70, no. 12, pp. 1458--1471, 1980.

....compressed image data. See Wallace [18] for more details on JPEG. 3.3 Image Dependent Approach The image dependent approach exploits the HVS s contrast and texture sensitivity. Some models based on this technique have been developed and employed by Watson [20] Daly [5] and Legge and Foley [9]. In this section, the author chooses to concentrate only on the models developed and used at AT T Bell Laboratory at Murray Hill, where he practiced his engineering internship. There are two perceptual masking threshold models already existing at AT T Bell Labs. The first one is incorporated in ....

G. E. Legge and J. M. Foley. Contrast masking in human vision. Journal of the Optical Society of America V. 70, pages 1458--1471, 1980.

....drops very quickly for chrominance. In the spatial domain, the first three frequency bands are used, since sensitivity is very low above 8 cpd. Those considerations are based on the work by Watson [10] 2.4. Masking The non linear transducer modeling of masking introduced by Legge and Foley [4] is used here. In this model, the detection threshold CT for a stimulus is computed as a function of the detection threshold of that stimulus in the absence of a masker, CT 0 (i.e. as given by the contrast sensitivity function) and the contrast of the masker CM . The relationship is given by Eq. ....

Gordon E. Legge and John M. Foley, "Contrast Masking in Human Vision", Journal of the Optical Society of America, Vol. 70, No. 12, pp. 1458--1471, December 1980.

....the visibility of a single stimulus. Masking accounts for the interferences between stimuli: part of the error will be masked by the background (i.e. the original image) and this will influence the perception of the noise. The model of masking that is being used here is the non linear transducer [5] depicted in Fig. 4. The detection threshold C T for a stimulus can then be computed as a function of the detection threshold of that stimulus in the absence of a masker, C T0 (i.e. as given by the contrast sensitivity function) and the contrast of the masker CM . The relationship is given by ....

Gordon E. Legge and John M. Foley, "Contrast Masking in Human Vision", Journal of the Optical Society of America, Vol. 70, No. 12, pp. 1458--1471, December 1980.

....to contrast is a function of the frequency and the orientation. This function is termed the contrast sensitivity function (CSF) ffl The adaptation to the local contrast of the background, i.e. visual masking. A model of visual masking that is commonly used has been proposed by Legge and Foley [5]. It sums excitation linearly over a receptive field. The formulation assumes that visual masking can only occur between two stimuli that belong to the same channel. Such modeling has been contradicted by experiments carried out by Foley and Boynton on simultaneous masking of Gabor patterns by ....

Gordon E. Legge and John M. Foley, "Contrast Masking in Human Vision", Journal of the Optical Society of America, Vol. 70, No. 12, pp. 1458--1471, December 1980.

....can be thought of as a spatial frequency filter bank with octave spacing of subbands in radial frequency, and angular bands of roughly 30 degree spacing. The presence of a signal component in one of these subbands will raise the detection threshold for other signal components in the same subband [27, 28, 29] and Chapter 1.3. The base masking threshold for each spatial frequency band is determined by a combination of the amplitude nonlinearity and the contrast sensitivity function. For the DC band March 14, 1999 7 (which corresponds to flat field images) this is the entire masking threshold. For ....

G. E. Legge and J. M. Foley, "Contrast masking in human vision," in Journal of the Optical Society of America, vol. 70.

....and 3 =4) and 2 temporal frequency bands, termed the sustained and transient mechanisms. An estimate of the CSF to coding noise, based on an excitatoryinhibitory formulation, has been obtained by psychophysical experiments [3] The model of masking used is the non linear transducer introduced in [1]. Watson and Ahumada proposed in [6] a model of the motion sensor considering the following fundamental properties of human motion sensing: ffl Humans perceive speed and direction of a movement. ffl Motion is local: humans are able to discriminate between objects moving at different speeds and ....

Gordon E. Legge and John M. Foley, "Contrast Masking in Human Vision", Journal of the Optical Society of America, Vol. 70, No. 12, pp. 1458--1471, December 1980.

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G. E. Legge and J. M. Foley, "Contrast masking in human vision," J. Opt. Soc. Am. 70, 1458--1471 (1980).

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G. E. Legge and J. M. Foley. "Contrast masking in human vision," Journal of the Optical Society of America. 70(12), 1458-1471 (1980).

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G. E. Legge and J. M. Foley, "Contrast masking in human vision," J. Opt. Soc. Amer. A, vol. 70, no. 12, pp. 1458--1471, 1980.

No context found.

G. E. Legge and J. M. Foley. "Contrast masking in human vision," Journal of the Optical Society of America. 70(12), 1458-1471 (1980).

No context found.

G.E. Legge and J.M. Foley,"Contrast masking in human vision," Journal of the Optical Society of America, 70(12), 1458-1471 (1980).

No context found.

Gordon E. Legge and John M. Foley, "Contrast Masking in Human Vision", Journal of the Optical Society of America, vol. 70, N 12, pp. 1458-1471, December 1980.

No context found.

Gordon E. Legge and John M. Foley, "Contrast Masking in Human Vision", Journal of the Optical Society of America, vol. 70, N 12, pp. 1458-1471, December 1980.

No context found.

G. E. Legge and J. M. Foley, "Contrast masking in human vision," Journal of the Optical Society of America 70, pp. 1458--1471, December 1980.

No context found.

Legge, G. E. and Foley, J. M., "Contrast Masking in human vision," Journal of the Optical Society of America, Vol. 70, pp. 1458-1470, 1980.

No context found.

G. E. Legge and J. M. Foley, "Contrast masking in human vision," Journal of Optical Society of America 70, pp. 1458--1470, 1980.

No context found.

Gordon E. Legge and John M. Foley, "Contrast masking in human vision", J. Opt. Soc. Am., 70(12): 1458-1471.

No context found.

G. E. Legge and J. M. Foley, "Contrast masking in human vision," J. Opt. Soc. Am., Vol. 70, pp. 1458--1471, 1980.

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