Based on plaintext information, a dynamic chaotic color image encryption algorithm is proposed as a solution for the security problem in image data transmission, Comparatively, the existing one has the characteristics of high key acquisition complexity and low encryption speed. Firstly, normalize the RGB components of the images so as to obtain the dynamic key associated with the plaintext, which encrypts images with any shape by rearranging and combining pixels from the original image. Secondly, the parameter offset key is introduced as the initial parameter of the logistic map to generate a high-precision chaotic encryption sequence. The chaotic value sequence is stored for disordered pixels according to the image size, and enlarged and rounded to enhance the pixel value diffusion of the original image. Finally, RGB components are fully fused and uniformly distributed to form a completely encrypted image. According to the experimental results and security analysis, the proposed algorithm is effective against differential attacks, with low complexity, high efficiency, and faster encryption speed.