Contrast enhancement of colour digital images

Abstract

Preliminary communicationThe main parts of digital images processing are procedures that improve the images quality which does not improve information content, but ensures that the image is visually better and more suitable for display. That is achieved through improved contrast, noise removing, sharpening and colouring pictures. Contrast is the rate of frequency changes in illumination and recording the difference between light and dark elements of the image in the brightness level. Contrast is the difference between two adjacent surfaces' brightness. Absolute value of the brightness of an object is of less importance than the relative brightness (contrast). Objects that have the same objective value of luminance may cause differences in the subjective sense of brightness depending on the contrast. This paper presents the improvement of the digital images quality in colour, which are the result of volcanic activity recording in the infrared region of the electromagnetic energy spectrum, with the application process to improve the contrast of images. High-quality digital images of the volcano were treated in high spatial resolution, which enabled the successful application of MATLAB and the results were very clear, precise and expressive images. Keywords: contrast; digital image; improving the quality; MATLAB; Plosky Tolbachik; volcano Poboljšanje kontrasta digitalnih snimaka u bojiPrethodno priopćenje Osnovna područja obrade digitalnih snimaka su postupci poboljšanja kvalitete snimaka, čime se ne popravlja informacijski sadržaj, već se postiže da slika bude vizualno kvalitetnija i pogodnija za prikaz, što se ostvaruje kroz poboljšanje kontrasta, otklanjanje šuma, izoštravanje i bojanje slike. Kontrast je mjera učestalosti promjene osvjetljenja na snimku i predstavlja razliku između svijetlih i tamnih elemenata snimka u nivou osvijetljenosti. Kontrast predstavlja razliku svjetline dviju susjednih površina. Apsolutna vrijednost svjetline nekog objekta je od manjeg značaja od relativne svjetline (kontrasta). Objekti koji imaju istu objektivnu vrijednost svjetline (luminance), mogu izazvati različit subjektivni osjećaj svjetline (brightness) zavisno od kontrasta. U ovom radu će biti predstavljeno poboljšanje kvaliteta digitalnih snimaka u boji, koji su rezultat snimanja vulkanske aktivnosti u infracrvenom području spektra elektromagnetne energije, uz primjenu postupka poboljšanja kontrasta snimaka. Obrađivani su kvalitetni digitalni snimci vulkana visoke prostorne rezolucije, što je omogućilo uspješnu primjenu programskog paketa MATLAB i dobiveni su vrlo jasni, precizni i izražajni slikovni prikazi.

TEMPEST Font Protects Text Data against RF Electromagnetic Attack

“…In this case the visual method was selected because graphic lines of video standards and laser printer were sources of valuable emissions. Moreover the visual method was supported by coefficient of inter-character correlation and values of CER [22]. The values of the inter-character correlation were calculated according to (3).…”