1. A bit rate control circuit for image compression, the bit rate control circuit comprising: a compression unit, used to perform a first quantization process on an image based on a linear quantization factor (LQF ini ) to obtain an initial number of bits per pixel (bbp ini ) and an initial number of zero coefficients (R ini ) are obtained; an R-value calculation unit calculating a target R value (R target ) after quantization based on the initial number of bits per pixel and a target number of bits per pixel (bpp target ); a linear quantization factor (LQF) calculation unit calculating a target linear quantization factor (LQF target ) based on the target R value (R target ); wherein a second compression is performed on the image based on the target linear quantization factor (LQF target ), to obtain a compressed image with respect to the target number of bits per pixel.