One-Dimensional Histogram for Color Images

Abstract

Histogram is an important information representation method which shows the distribution of the pixels in digital images. In this context, one-dimensional array is processed in gray level images whereas it is necessary to analyze three-dimensional array in color images. Therefore, the computational cost of histogram processing in color images is high. Combining the one-dimensional histogram information from each channel is also a problem. In this study, a new technique was developed to produce a one-dimensional histogram by using the Red-Green-Blue (RGB) color space for color images. In the proposed approach, thresholds are first obtained for each channel using Otsu and Kapur thresholding methods, and then the color space is divided into 8 prisms by means of the thresholds. The remaining pixels in the generated prism are clustered by assigning into the same class. In addition, the color reduction is done by using the average value of the pixels included in the same class. The loss of information in the images reduced is evaluated by the Peak Signal Noise Ratio (PSNR) criterion.

Keywords

• RGB Color Space
• Histogram
• Thresholding
• Color Reduction

Renkli Görüntüler İçin Tek Boyutlu Histogram

Abstract

Histogram sayısal görüntülerdeki piksellerin dağılımını gösteren önemli bir bilgi temsil yöntemidir. Gri seviyeli görüntülerde tek boyutlu dizi işlenirken, renkli görüntülerde üç boyutlu dizinin analizinin yapılması gereklidir. Dolayısıyla renkli görüntülerde histogram işleminin hesapsal maliyeti yüksektir. Her kanaldan alınan tek boyutlu histogram bilgisinin birleştirilmesi ise ayrıca bir problemdir. Bu çalışmada renkli görüntülerde Kırmızı-Yeşil-Mavi (KYM) renk uzayı kullanılarak tek boyutlu histogram üreten yeni bir teknik geliştirilmiştir. Önerilen yaklaşımda, öncelikle her kanal için Otsu ve Kapur eşikleme yöntemleri kullanılarak eşikler elde edilmiş, akabinde renk uzayı söz konusu eşikler yardımıyla 8 adet prizmaya bölünmüştür. Oluşturulan prizma içerisinde kalan pikseller aynı sınıfa atanarak kümeleme yapılmıştır. İlave olarak aynı sınıfa dâhil olan piksellerin ortalama değeri kullanılarak renk indirgemesi yapılmıştır. Böylece elde edilen görüntülerdeki bilgi kaybı tepe sinyal gürültü oranı (Peak Signal Noise Ratio: PSNR) ölçütü ile değerlendirilmiştir.

Keywords

• KYM Renk Uzayı
• Histogram
• Eşikleme
• Renk İndirgeme

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