A multi-hole direct injection injector was studied by means of image analysis. Methodologies based on an automatic process of cone angle measurement and edge detection were applied for the spray images generated by a 100 bar injection pressure discharged into a pressurized rigid chamber. A criterion based on pixel values was taken to localize the spray edges as angular coordinates and also with x and y position data. The high pixel values were associated with liquid phase while the low pixel values were associated to its absence. Computational codes written in MATLAB environment were used to analyze the numerical matrices associated to the images. Using the written MATLAB codes, a comparison of the effect of atmospheric back pressure, inside the chamber, on the spray pattern, cone angle and spray penetration were evaluated. The chamber was pressurized with 2.5, 5.0, 7.5 and 10 bar of back pressure. The tested fluid injected was EXXSOL D60 for simulating ethanol fuel behavior. A simulated engine speed rotation of 2400 rpm and 3% duty cycle were set in Motec ECU. With this configuration, a pulse of 1.5 milliseconds with spray injection followed by a period of 48.5 milliseconds without injection is obtained. The images were obtained with continuous back illumination and a CCD camera for recording frames with 6504 Hz. The injection pressure was fixed in 100 bar.